Variable effect absorption machine and process

A thermal machine includes a horizontal rotatable shaft extending through a cylindrical housing which contains the at least high and low pressure stages. The shaft carries a pair of cylindrical drum heat transfer means within the housing to rotate with the shaft. All or part of both drums contain an intermediate pressure stage, with pool collection capability within the drums using annular rims to retain the absorbent solutions. The outer housing has means to permit collection of absorbent solutions in separate pools in contact with the respective outer sidewall surfaces of the drums. Such contact provides thermal coupling between stages. Additional sections of the drums may contain pools for external circulants, which drum sections also contact the pools in the outer housing. Sealing means permits rotation of the respective drum means but isolates the vapors within the drums from the pools within the outer housing and vapors from the outer housing pools from one another. Piping is provided for the flow of an absorbent solution among the vessels in different stages and conduits may permit vapor flow from one vessel to a second within a stage. In some applications, the drum may be corrugated and wiped for enhanced heat transfer.

The present invention concerns a novel thermodynamic cycle or a family of 
cycles and a machine or group of machines which embody processes using the 
cycles to produce a cooling, heat pumping, or temperature amplification 
effect. Certain specialized versions of the machine may be coupled with 
additional equipment to produce shaft power or to operate separation 
processes such as desalination. 
The novel process is known as variable effect absorption. The variable 
effect absorption process is so named because a variable amount of the 
absorption subprocess heat is transferred to the generation subprocess. It 
offers two characteristics superior to prior art processes. First, the 
process may function as single effect, double effect, or any state between 
those extremes so that it adapts to variable conditions of operation. 
Second, heat exchange pinch effects typical of the prior art and which 
damage efficiency, decrease utilization and increase auxiliary power needs 
are very small for the variable effect process. The machine may employ a 
novel rotating counterflow heat exchanger designed to provide the maximum 
benefits from these process characteristics. The significance of this is 
explained below in terms of examples. 
PRIOR ART 
In the prior art there have been a multitude of theoretical and real 
thermodynamic processes familiar to heating, air conditioning, and 
refrigeration engineers and to those involved in related areas such as 
power generation, or desalination. Both single effect and double effect 
absorption processes have been known. The single effect process has been a 
process involving a single loop usually with a single two component fluid 
undergoing change of state and concentration and heating and cooling in 
the course of the process. Double effect processes have involved one or 
two such loops which may employ the same or different fluids sometimes 
confined to their own loops, but having heat exchange relationships 
between the two loops such that the effects of the process of one aids in 
the process of the other and vice versa. Many possibilities of 
intermediate solution situations exist, too, such as where one of the 
loops is open rather than closed. Within these processes vapors are 
generated at one constant pressure and absorbed at a second different 
pressure. This is true also for Rankine processes, in which the fluid is 
usually a single material and the difference in pressure of vapors is used 
to drive a Rankine converter for power generation or is created by a 
Rankine converter for a heat pumping or chilling effect. 
In the prior art there have been theoretical and practical limitations on 
the efficiency of such processes. The absorption processes have been 
confined to relatively fixed temperature differences between input and 
output stations for their practical effects with different ranges being 
achieved by different kinds of fluids. Different kinds of fluids are 
employed in order to achieve desired heat input and output temperatures 
determined particularly by the boiling points of the selected fluid and, 
in some instances, the freezing point, and not independently selectible 
for optimal matching to specific applications. 
The prior art processes, including both absorption and Rankine processes, 
have their performance degraded by pinch effect penalties which result 
from their being designed to operate with constant temperature sources and 
sinks. Heat exchange pinch effects penalize performance, equivalent to 
decreasing the source temperature and increasing the sink temperature, and 
efforts to decrease the penalties result in limitations on utilization of 
the heat source and sink, and in increased auxiliary requirements. For 
example, suppose an application uses hot waste water which is run through 
a heat pump or other machine then discarded. For processes designed for a 
constant temperature source, the effective input temperature for 
calculating theoretical efficiency is the leaving temperature of the water 
(minus a heat exchange approach temperature difference). If the leaving 
temperature were made low (near ambient) in order to utilize a large 
amount of heat from the waste water, the process efficiency would be low. 
If the leaving temperature were only 10.degree. to 20.degree. F. less than 
the entering temperature, process efficiency is only slightly damaged, but 
little heat is recovered from the waste stream. In determining a 
compromise temperature drop, auxiliary power is also a consideration. The 
smaller the temperature drop or rise, the greater are the flows of 
external fluids needed for a given heat input or output. External 
electrical power for pumps and/or fans is particularly a large fraction of 
total energy input in many space heating and cooling applications, and 
especially for those using air cooled prior art absorption equipment. 
THE NATURE OF THE PRESENT INVENTION 
In accordance with the variable effect of the present invention, the amount 
of heat transferred from the absorber to the generator, and hence the 
coefficient of performance is determined by the temperatures of the heat 
sources and heat sinks. The adaptability of the variable effect process to 
independent variation of input and output temperatures is particularly 
advantageous for applications using an ambient heat source or sink e.g., 
respectively, for heat pumping or for cooling and power generation, since 
the ambient temperature varies seasonally. It is also an advantage for 
applications using a waste or solar heat source which seasonally varies in 
temperature, or which may vary from one specific installation to another. 
Use of the variable effect permits a high fraction of theoretical 
performance to be achieved with broad ranges of independent variation in 
those temperatures. That is, if temperature conditions become more 
favorable, the variable effect process is able to take advantage of the 
change to achieve better performance. The state-of-the-art absorption 
processes do not, and cannot respond with improved performance as does the 
variable effect process. For example, operated with solar or waste heat, 
the machine automatically adjusts to changing heat input and/or rejection 
temperatures to maintain a high fraction of theoretical performance, which 
cannot be achieved with the conventional machines. Used with fossil heat 
alone, the seasonal heating and cooling performance is better than with an 
electric heat pump or furnace, so that a back-up heating and cooling 
system would not be needed if the machine were used with a small solar 
collector array. For another example, the annual power generated from 
waste heat sources is increased by use of the variable effect process 
because optimal benefits are derived from seasonal variation in the 
ambient sink temperature. 
The variable effect process also accepts and rejects heat over large ranges 
of temperture. This variable response permits small heat exchange pinch 
effects, i.e., a better match to sensible heat sources such as solar or 
waste heat and to sensible sinks such as ambient or conditioned air. 
Therefore, referring to the waste heat example in prior art above, the 
leaving temperature may be closer to ambient and a good fraction of heat 
is recovered. The efficiency is determined by the log mean input 
temperature (approximately the arithmetic mean), not the leaving 
temperature. Therefore, both efficiency and utilization, the fraction of 
heat recoverable, are higher for the variable effect than for other 
processes. Pumping power for the variable effect machine is smaller 
because of the larger temperature ranges through which fluids are cycled. 
This applies to solution pumps and to pumps or fans for the heating and 
cooling circulants. 
A large range of input temperature also permits a simultaneous heat input 
from solar or waste heat at a low temperature and auxiliary (fossil) heat 
at higher temperature. As a consequence, for example, that solar cooling 
can be accomplished with a great variety of collector array sizes and 
types, and which need not be designed for the requirements of the more 
rigid thermal processes of conventional machines. 
Preferred embodiments of the process equipment use a rotary drum heat 
exchanger on which an absorption fluid releases and absorbs the volatile 
absorption fluid component. This device may be used with the variable 
effect or other absorption processes. The advantages of the device are 
obtained through integration of the following requirements of absorption 
equipment: 
1. Structurally efficient staging and mechanical support is provided by 
using a drum as a structural member which separates the housing volume 
into two isolated volumes. Circumferential extending of the drum means 
adds strength and rigidity and permits the use of a light-weight 
thin-walled drum which also enhances heat transfer across the wall; 
2. Control of fluid volume mixing for thermodynamic efficiency is provided 
by segmentation with the circumferential extensions of the axially 
counterflowing fluid volumes; 
3. Uniform absorbent fluid distribution as films for efficient mass 
transfer with vapor is provided by rotation of the drum continuously 
through the absorption fluid gravity pool(s) and vapor volume(s); 
4. Compactness is provided by drums designed with extended surface areas 
many times the plain cylindrical area. 
Use of this invention to integrate these functions in absorption machines 
provides the following advantages compared to the prior art: 
1. Easier mass-fabrication and assembly of equipment and improved 
reliability due to its single unit construction and due to formation of 
the basic extended-surface drum by efficient mass-production techniques, 
for example, by hydraulic forming of corrugations, by continuous welding 
of helical fin or by press-fitting or circular fins; 
2. Easier shipping and installation due to its compactness and lower 
weight, resulting from the strengthening by the extensions and the 
inherently compact geometries; 
3. Reduces requirements for materials due to its saving of separate parts 
otherwise needed for the various functions it serves, due to its light 
weight, due to high heat transfer coefficients resulting from optimal 
fluid velocities, and due to improved thermal efficiency, as described 
below, which reduces the heat throughput required per unit of output; 
4. Improved energy efficiency due to segmentation of fluid flows to provide 
true counterflow over large temperature ranges, and for other reasons 
given below. 
In the prior art there are well known penalties for temperature crossing, 
which apply to any multi-pass heat exchanger which is not true 
counterflow. The benefits of counterflow heat exchange for single effect 
absorption air conditioning are well known in the art, discussed for 
example in the Proceedings of the 1979 ASHRAE annual meeting. The large 
temperature and concentration ranges which may be employed without 
crossing penalties using this invention, and which are not practical using 
the prior art, reduce the required absorption fluid flow rates per unit of 
desired effect (recirculation rates) and reduce solution heat recovery 
needs, pumping power and thermal penalties for heat exchanger 
effectiveness. Furthermore, the flow rates of the external fluid heat 
source or heat sink or both can also be reduced by using large temperature 
ranges for the absorption boiling and condensing processes, which is 
particularly desirable for saving fan power for devices such as an exhaust 
gas heated generator or air cooled absorber. 
Very large energy efficiency improvements and large savings in heat 
exchanger area can be achieved using the rotating drum heat exchanger with 
certain advanced absorption cycles, those for which heats must be 
transferred between two absorption fluids in separate pressure stages. 
Examples of these are the "fat" single effect (or GAX) cycles, the common 
condenser double effect cycle, the regenerative single effect cycle, and 
the regenerative double effect cycle, as well as the variable effect 
cycle. 
In the prior art, what now appears to be an erroneous conclusion had been 
reached based upon the nature of processes in currently available 
equipment. The assumption was that the countercurrent absorber arrangement 
must inevitably involve an intermediate fluid to exchange heat between the 
absorber and generator. This was assumed because, within the conventional 
vertical absorber, liquid travels downwards under the influence of gravity 
as the vapor is absorbed, establishing a temperature profile which 
increases from bottom to top. This temperature gradient is in conflict 
with that established in the generator, which also uses gravity to drain 
the liquid, and, so, therefore, an intermediate fluid was assumed to be 
required to match the gradients. 
The present invention negates the conclusion that an intermediate sensible 
heat transfer fluid is needed to transfer heats between two absorption 
fluids (one boiling and one condensing). With the rotating drum means of 
the invention being horizontal and rotating through pools, absorption 
fluids may flow counter to each other, inside and outside of the drum, 
each through its own isolated vapor space. This permits saving the costs 
of the intermediate loop equipment, auxiliary energy for the loop flow and 
two thermal performance penalties for transfer between a 
boiling/condensing fluid and a sensible fluid (pinch effects). Large 
savings in the heat exchanger area are achieved because two sensible heat 
transfers with an intermediate fluid are replaced by one 
boiling/condensing transfer. The fat single effect cycle with an open 
evaporator has been mentioned in the art as being of particular interest 
for separation applications such as desalination, waste water clean-up, 
product drying or concentrating or solvent recovery. In these applications 
and with the device of the present invention, as much as 90% of the 
generator heat can be provided by transfer from the absorber across the 
rotating heat exchanger, over a fluid temperature span of about 
200.degree. F. Compared to the use of an intermediate fluid, the 
invention saves 80% of the primary heat exchange surface. The common 
condenser double effect cycle has been described in the literature of the 
art as being of particular interest for space heating and cooling. It 
achieves the highest performance and lowest heat exchanger area 
requirement per unit of desired effect of any of the known double effect 
cycles. With this cycle and the device of the present invention about 33% 
of the primary surface area can be saved compared to the same cycle in a 
machine using an intermediate fluid. The performance improvements for 
applications of the variable effect cycle to space heating and cooling, 
refrigeration, heat upgrading and others have been mentioned above and 
will be explained further below in the description of the drawings. 
Without the rotating heat exchanger and absorption fluid vapor absorbing 
and releasing device, the variable effect process would require two 
intermediate fluid loops for internal heat transfer. 
The rotating counterflow heat exchanger is a horizontally oriented drum in 
contact with liquid gravity pools and vapor spaces on its inside and 
outside surfaces, such that continuously received absorption fluids on the 
inside and outside of the drum can exchange heat with each other and can 
absorb or release the volatile fluids within their respective vapor 
spaces. This configuration solves an outstanding problem recognized in the 
prior art as a limitation on the application of various advanced 
absorption cycles, and including the variable effect cycle disclosed 
herein, which require internal heat transfer between two absorption 
fluids. The device is energy efficient and compact with circumferential 
surface extension and saving of materials through use of thinner gauges of 
metal. It is more easily produced than absorption process heat exchangers 
of the prior art. It is also particularly advantageous in certain 
embodiments employing surface extension for use with sensible fluids 
including air or liquids in exchanging heat between these and absorption 
fluid and permiting the efficient absorption or release of vapor from the 
absorption fluid to the vapor space(s) defined by the drum and its 
housing. 
GENERIC DESCRIPTION 
A machine of the present invention is comprised of three pressure stages, 
each containing an absorbent fluid from which gas or vapor is evolved 
and/or into which gas or vapor is absorbed. Gas or vapor flows from a 
regenerator to a resorber in an intermediate pressure stage. The heat for 
the regenerator may be provided by the absorption of vapor in the 
absorber, which is located in a second pressure stage, and heat provided 
by the resorber may be transferred to the generator in a third pressure 
stage. Means are provided for the flow of absorbent fluid through and 
among the generator, absorber, regenerator and resorber, for the flow of 
gas or vapor between the regenerator and resorber and to the absorber and 
from the generator, and for the transfer of heat to, from, and among 
these. The amount of gas or vapor produced by the generator is ultimately 
absorbed by the absorber at the same rate, thus providing for steady state 
operation of a process cycle. The gas or vapor has different thermodynamic 
potential in the second stage containing the generator and the third stage 
containing the absorber on account of their different pressures; thus, as 
gas or vapor is transferred, work of several kinds may be produced or used 
by the machine, so that it may serve many purposes. 
A machine in accordance with the present invention in various modifications 
may be used for fuel fired, solar, or waste heat actuated heat pumping, 
refrigeration or temperature amplification or for desalination or other 
separation processes. Other modifications permit use of the process for 
improved efficiency of power generation, especially with solar, waste 
heat, and ocean thermal sources, or for improved performance of 
compression (electric) heat pumps. 
For example, the machine may contain an evaporator within the same pressure 
stage as the absorber and a condenser within the same pressure stage as 
the generator; so that, the machine may serve for heat pumping, 
refrigeration, temperature amplification, or desalination and other 
separation processes. The evaporator and condenser may use a component of 
the absorbent fluid (pure liquid refrigerant), an absorbent fluid of the 
same or different composition from that used in the generator or absorber, 
or liquids on which separation work is to be performed; in all cases the 
liquid in the evaporator and condenser must contain at least the condensed 
state of the gas or vapor transferred to and from these components. 
A machine of this type is comprised of three pressure stages, each 
containing absorbent solutions in which vapor is condensed and evolved. 
Thus, vapor flows from a generator to a condensor in one stage, from a 
regenerator to a resorber in a second stage, and from an evaporator to an 
absorber in a third stage. Excepting the evaporator and condenser in one 
favored version of the machine, the vessels are provided with a flow path 
for the absorbent solution and means for counterflow heat exchange with a 
second fluid. The second fluid may be a sensible heating or cooling 
circulant or absorbent solution in a different pressure stage. Various 
heat exchangers may be used for the recovery of sensible heat from vapor, 
liquid refrigerant, and solutions. 
For a second example, the machine may contain a Rankine converter through 
which the gas or vapor is passed between the generator and absorber 
containing pressure stages; so that, the machine may serve for power 
production, or for production of heating and cooling effects by mechanical 
means, such as augmentation of the performance of electrically driven heat 
pumps or refrigeration equipment. These configurations permit the Rankine 
subprocess to be matched to sensible heat sources and sinks for improved 
performance. 
Compared to conventional single effect absorption machines, the variable 
effect machines require relatively more heat exchange capacity and an 
additional pressure staging. This is true also for the conventional double 
effect machine. For example, the solar cooling version of the machine 
requires about one-quarter additional heat exchange capacity to be 
accomplished per unit of output compared to single effect machines. 
However, improved performance should readily compensate the added hardware 
and installation costs, if any, because it permits a much greater benefit 
to be achieved from the investment in solar collectors. A novel approach 
to heat exchange is also offered, the increased efficiency of which may 
more than compensate for the additional heat exchanging capacity 
requirement without requiring additional heat exchange surface. 
In one most simple but less effective version of the machine the second 
fluid heating circulant flows from the heat source to the generator, to 
the resorber, and back to the heat source; and a cooling circulant flows 
from the heat sink to the absorber, to the regenerator, and back to the 
heat sink. Conventional stationary heat exchangers are used in this 
version. 
In a second version of the machine, a rotating heat exchanging cylinder 
containing the regenerator and resorber at intermediate pressure contacts 
portions of the absorber and generator fluid flows, so that its wall is 
continuously coated with solutions on both sides which flow parallel to 
the rotation axis. 
A third favored version of the machine extends the rotating heat exchanger 
to include all of the absorber and generator. Other versions of the 
machine use two such cylinders to accomplish heat exchange with the 
evaporator and condenser as well. 
The rotating heat exchanger permits the unique potential for small heat 
exchange pinch penalties of the variable effect machine to be fully 
realized in practice.

EXPLANATION OF THE VARIABLE EFFECT PROCESS 
FIG. 1 is an illustration by which the response of a machine using the 
variable effect process can be compared with those of machines using 
single or double effect processes. 
Referring now to FIG. 1, generator maximum temperature is plotted against 
instantaneous coefficient of performance (hereafter sometimes referred to 
as COP) for cooling for prior art processes and the variable effect 
process. The variable effect process is represented by the solid line 10. 
It will be seen to extend from a relatively low temperature to a 
relatively high temperature and over a substantial portion of its range to 
be above 65 percent of Carnot coefficient of performance which is 
illustrated by the dashed line 12. A comparison is made with various prior 
art techniques. Specifically, commercial lithium bromide-water machines 
are illustrated by plots 14 and 16. The plot 14 for the single effect 
machine using this solution is shown to have a relatively low generator 
temperature, whereas the plot 16 for the double effect machine lies at a 
relatively high temperature. The temperature range of efficient operation 
in each case is obviously quite limited compared with that of the variable 
effect machine. A plot 18 for a further single effect machine employing 
commercial ammonia-water solution has a different temperature range from 
that of the single effect machine using commerical lithium bromide-water, 
but is equally limited. Lithium bromide-water or ammonia-water or other 
fluids may be used in the variable effect machine. These curves assume a 
minimum temperature of 110.degree. F. in the condenser and absorber and 
40.degree. F. in the evaporator. 
The variable effect process is seen to provide increased performance as the 
generator temperature is increased, maintaining approximately 65 percent 
of Carnot efficiency (plot 12); single and double effect processes achieve 
that efficiency only at a single optimum generator temperature. Similar 
behavior is observed for variations in the reject (condenser and absorber) 
or cold source (evaporator) temperature. 
The penalties resulting from heat exchange pinch effects are not apparent 
from FIG. 1, but have been explained above. 
There have been recent efforts, by Carrier Corporation, for example, to 
improve the single effect process by using counterflow heat exchange for 
generation and absorption and thereby to reduce pinch effects. However, 
the improvement is minor compared to that of the variable effect process 
because the temperature range used is only about a third of that for the 
variable effect, and because the machine coefficient of performance is, to 
a first approximation, not improved by absorbing some of the heat at a 
higher temperature (i.e., COP versus temperature is still of the form for 
the single effect process of FIG. 1). Kim Dao, Lawrence Berkeley 
Laboratory, University of California, has described two new absorption 
processes, "single and double effect regenerative cycles", which respond 
to variations in source and sink temperature much as the variable effect 
process. However, the regenerative cycle heat inputs and outputs are 
effectively at constant temperature, so that heat exchange pinch effects 
are not reduced, and the equipment required is extremely complex compared 
to the variable effect machine. 
The two broad classes of the variable effect process are illustrated by 
FIGS. 2 through 5. At each of three constant pressures vapor, or gas, is 
transferred from a generating (boiling) to a condensing solution at a high 
pressure, from regeneration to resorption at an intermediate pressure, and 
from evaporation to absorption at a low pressure. Reverse operation of the 
process is also possible, where the vapor or gas is transferred from a 
generating to a condensing solution at low pressure and from evaporation 
to absorption at high pressure. Absorption working fluids or components of 
the fluids (i.e., gas, vapor or liquid refrigerant) flow from subprocess 
to subprocess as indicated in FIGS. 2 and 4. Sensible heat recovery from 
these flows will be described, but are not included in the figures to 
avoid confusion by the added legends. The thermodynamic states 
(concentration, temperature, and vapor pressure) of the solution before 
and after treatment at each subprocess are indicated by consecutive 
numbers in the thermodynamic cycles of FIGS. 3 and 5. These correspond to 
the same numbers in the process flow sheets of FIGS. 2 and 4, following 
the usual convention for mapping thermodynamic cycles to processes. The 
same numbering convention is used in describing operation of a variable 
effect machine below. FIGS. 3 and 5 are thermodynamic cycles for an 
idealized fluid. The process may be used with any actual absorption fluid. 
Calculations have been performed for lithium bromide-water, 
Supersalt-water, water-ammonia, and sodium thiocyanate-ammonia to confirm 
estimates in plot 10 of FIG. 1. Other fluids containing methanol or R-22 
have been considered. Ammonia-water or R-22 with organic amides such as 
dimethylhexamide or 2-pyrrolidone may be particularly attractive for using 
the variable effect process with a Rankine converter as discussed below. 
In addition to these fluid which release condensible vapors on heating, 
fluids containing dissolved gases, such as ethanolamines-carbon dioxide, 
soluble carbonates-sulfur dioxide, metal complexes-hydrogen, etc., could 
be used with the process for special purposes, such as separation and 
purification of gases or gas containing liquids. 
FIG. 2 is a block diagram showing a heat pumping or chilling process using 
a single fluid loop which can be reversed by changing the functions from 
those shown in the boxes without parentheses to those shown in the same 
box within parentheses. A temperature amplification effect (the reverse 
effect) is obtained with the same subprocesses and interconnections as the 
former by reversing the direction of all heats and solution flow, and 
changing the FIG. 2 names given to the subprocesses to those in 
parentheses. The distinction between heat pump and chiller is made 
according to the identity of the external circulant heat sources and sinks 
for a specific application; the process is identical. For example, q hot 
may be the input from a fuel fired boiler ; q cold, the input from 
ambient; and q reject 1 and q reject 2 the outputs to a conditioned space; 
the process then is described as heat pumping. Or q cold may be the input 
from a conditioned space and q reject 1 and q reject 2 the output to 
ambient. The process then is chilling or air conditioning. In applying the 
process for separation, as will be described below, the process remains 
formally a heat pumping process, though heat is not then the product of 
interest. 
In the heat pumping or chilling mode, externally supplied heat q hot is 
applied to the generator stage 20. Fluid is circulated from generation to 
the resorption stage 22 from which heat, q transfer 2, is removed to the 
generator, displacing some external heat input. Following this the fluid 
moves to the absorption stage 24 where heat is given up in part to the 
regeneration stage, q transfer 1, and in part rejected to an external 
circulant, q reject 1. The fluid is then circulated to the regeneration 
stage 26 and back to the generation stage 20. Within this absorbent loop 
vapor flows at intermediate pressure from the regeneration stage 26 back 
to the resorption stage 22. Outside the absorbent solution loop vapor at 
high pressure is transferred from generator 20 to a condensation stage 28 
in which condensation to liquid refrigerant occurs at 28 due to a cooling 
effect supplied by an external circulant, q reject 2. Refrigerant moves 
from the condensation unit 28 to the evaporation unit 30 from which vapor 
at low pressure is produced by heat input, q cold, from an external 
circulant and transferred to the absorption section 24 of the main loop. 
By FIG. 3 it is shown that changes in concentration of refrigerant in the 
absorbent fluid occur at each subprocess. Further, the magnitude of 
concentration change as indicated by the lengths of the horizontal 
intervals roughly correspond to the relative magnitudes of the heat 
effects associated with each subprocess. Thus, from state 1 to state 2 the 
fluid is depleted or refrigerant as heats q transfer 2 and q hot are 
sequentially input to the generation subprocess. From state 2 to state 3 
the fluid is sensibly cooled without change in concentration so that it 
may be the proper (equilibrium) temperature for use in resorption. In 
resorption from state 3 to state 4 refrigerant is gained by the fluid and 
the heat of resorption, q transfer 2, is created. From state 4 to state 5, 
further sensible cooling occurs prior to absorption. In absorption, heats 
q transfer 1 and q reject 1 are removed as the refrigerant concentration 
is increased to state 6. The fluid is then sensibly heated to state 7, and 
from there to state 8 it losses refrigerant as the heat q transfer 1 is 
accepted by regeneration. Finally, the fluid is sensibly heated to state 
1, thus completing the cycle. The condensation and evaporation 
subprocesses operate with pure refrigerant, indicated as an infinite 
concentration of refrigerant. Here heats are not associated with a change 
in concentration, but only a change in state from liquid to vapor or 
vice-versa. 
The process of FIGS. 2 and 3 includes four subprocesses which operate over 
ranges of temperature and two processes, condensation and evaporation, 
which operate (effectively) at constant temperature. This is apparent from 
FIG. 3. Heat exchange pinch effects are small for the four former 
subprocesses and large for the two latter subprocesses, except when these 
are coupled with or replaced by a Rankine subprocess, as will be 
discussed. Thus, although substantial improvement in reducing pinch effect 
penalties compared to state-of-the-art processes is obtained, there 
remains an opportunity for further improvement. 
FIG. 4 illustrates an example of a further variable effect process in which 
there are two absorption fluids in separate loops. The first loop has a 
generator 32 feeding a resorption stage 34 and finally being fed to a an 
absorption stage 36 from which, it returns to the generator 32. The second 
fluid or solution is passed from a condensation stage 38 to a regeneration 
stage 40, thence, to an evaporation stage 42, whence it is returned to the 
condensation stage 38. Heat applied at the generation stage 32 generates 
vapor at high pressure which is transferable to the condensation stage 38. 
Regenerator 40 provides vapor at intermediate pressure to flow to 
resorption stage 34. Vapor at low pressure generated at the evaporator 42 
may flow to the absorption stage 36. FIG. 5d shows the concentration 
changes associated with the subprocesses. Numbers are again applied to 
each solution state to permit comparison of the process with the 
thermodynamic cycle. 
Again, FIGS. 4 and 5d should be considered together to better understand 
the variable effect using two separate absorption working fluids. With the 
regeneration and resorption subprocesses operating with different fluids 
in this case all subprocesses operate over ranges of temperature, and all 
pinch effects are small. The heat, vapor, and solution directions for this 
process are also reversible for different effect. There are eight ways of 
arranging the subprocesses and solution flows illustrated in FIGS. 5a-5h 
so that regeneration and resorption are in different fluid loops. With the 
example as taught by FIGS. 4 and 5d, the other arrangements become obvious 
to one skilled in the art from illustrated cycles. There are seven 
arrangements of thermodynamic cycles additional to that of FIG. 5d 
presented in abbreviated form. The two approaches, i.e., the single fluid 
loop of FIGS. 2 and 3 and the double fluid loop of FIGS. 4 and 5, offer 
different advantages and disadvantages for various applications. In order 
to provide minimum recuton in pinch effect penalties a double loop is 
preferred. But a single loop minimizes equipment requirements, and would 
therefore be preferred for many applications. 
For those applications in which performance is most highly prized, i.e., 
those employing the most expensive heat sources such as solar applications 
or fuel oil used in remote locations, there are particular double loop 
processes which may be preferred for specific operating conditions. Thus, 
the process of 5d provides a high COP cooling or heat pumping by taking 
advantage of a high temperature of q cold; the process of 5g provides a 
high COP cooling or heat pumping by taking advantage of a high temperature 
of q hot; the process of 5c (in reverse mode) provides a high COP for 
temperature amplifying by taking advantage of a high waste heat 
temperature (T reject) and low reject temperature (T cold); the process of 
5h provides a high COP for temperature amplifying by taking advantage of a 
low reject temperature (T cold) and low amplified temperature (T hot). 
Processes 5a and 5f permit a high T hot to be traded against a low T cold 
without a decrease in COP cooling or heat pumping. Conventional absorption 
processes do not permit such trade-offs. Process 5b permits a high reject 
temperature to be traded against a high T cold without loss in COP cooling 
or heat pumping. Process 5e permits a low T hot to be traded against a low 
T reject without loss in COP cooling or heat pumping. It is apparent that 
a single machine can be used to serve any of the FIG. 5 processes, since 
they differ only in three respects not requiring different equipment. 
These differences are: (1) the location of the regenerator and resorber in 
one or the other of the two fluid loops (equipment of the regenerator and 
resorber are identical); (2) the direction of fluid flow within each of 
the loops, which are independently selectible (and accomplished with 
suitable valving); and (3) the temperatures of the externally supplied 
heating and cooling circulants and the subprocesses to which these are 
directed. However, the latter are most efficiently accomplished with heat 
exchange area and design specific for the temperature range to be 
accommodated, so that different machines for the different FIG. 5 
processes are preferred. The design (that is, chiefly, length requirement) 
of particular heat exchange sections for the various temperatures, 
depending chiefly on the viscosity and change in connection with 
temperature characteristic of the absorption fluid used is well understood 
to those practiced in the art, and is not a subject of this invention. 
Returning to the variable effect process of FIGS. 2 and 3, these can also 
be employed as part of a larger process in which the high pressure and low 
pressure vapor flows interact with a Rankine converter. The converter may 
be a turbine, reciprocating converter, or a compressor. The converter may 
replace the condenser and evaporator of FIG. 2 or an additional condenser 
and an evaporator in series with a converter may be provided with the 
second condenser thermally coupled to the variable effect evaporator, and 
the second evaporator thermally coupled to the variable effect condenser. 
The additional condenser and evaporator permit use of a different working 
fluid with the Rankine converter than is used with the variable effect 
absorption process itself. With the former arrangement with no evaporator 
or condenser the variable effect process provides a source and sink for 
vapors at constant pressure by accepting and rejecting heat over ranges of 
temperature. With the latter arrangement the variable effect process 
provides a source and sink for heats at constant temperature (the Rankine 
condenser and evaporator) from an external source and sink available over 
ranges of temperature. That is, the variable effect absorption loop acts 
as a sensible/latent heat converter which augments the Rankine process. In 
both cases the benefits of the variable effect process are to greatly 
reduce pinch effects and to increase source and sink utilization compared 
to state-of-the-art Rankine processes, as was previously discussed for 
waste heat temperature amplification. Examples of process flow sheets for 
power production are FIG. 2 with a Rankine turbine replacing evaporation 
and condensation, and FIG. 2 with the addition of a Rankine evaporation 
subprocess coupled to condensation, a turbine, and a Rankine condensation 
subprocess coupled to evaporation. Examples of process flow sheets for 
pumping heat available over a range of low temperatures to heat available 
over a range of higher temperatures are FIG. 2 in the reverse mode with a 
Rankine compressor replacing evaporation and condensation and FIG. 2 in 
the reverse mode with the addition of a Rankine evaporation subprocess 
coupled to condensation, a compressor, and a Rankine condensation 
subprocess coupled to evaporation. 
The process of FIGS. 2 and 3 can also be employed as part of a larger 
open-cycle separation process, for example, desalination. For this 
example, ocean water evaporation can replace the evaporation subprocess of 
FIG. 2, and the product water produced by condensation is removed instead 
of conducting it to evaporation. For this case, evaporation and 
condensation are thermally coupled, the heat for the former being provided 
by the latter. 
Summaries of the applications for these several arrangements of the 
variable effect process that have been discussed are given below, together 
with the machines that would use them, and the benefits the variable 
effect process provides compared to state-of-the-art alternatives. 
TABLE I 
__________________________________________________________________________ 
Benefits of the 
Machine Application Variable Effect Process 
__________________________________________________________________________ 
Heat pump/chiller 
Fuel-fired space 
Reduced pinch effects, 
heating or cooling 
improved seasonal adapta- 
tion and performance, 
reduced power requirements 
for circulation of fluids 
Heat pump/chiller 
Solar and fuel fired 
As above, permits simul- 
space heating or 
taneous solar and fuel 
cooling energy input in any ratio 
the instantaneous solar 
capacity permits 
Heat pump/chiller 
Ocean temperature 
Ocean water never heated, 
with coupled 
difference actuated 
reduced number of pressure 
evaporator/conden- 
desalination or fuel 
stages for equivalent per- 
ser heat exchanger 
fired desalination 
formance to other thermal 
desalination processes 
Heat pump/chiller 
Waste heat Reduced pinch effects, 
with reversed heat 
temperature reduced power requirement 
inputs and outputs 
amplification 
for circulation of fluids, 
increased utilization of 
heat source, improved 
seasonal adaptation and 
performance 
Latent to sensible 
Electric heat pump 
Reduced pinch effects, 
heat converter 
performance improve- 
reduced power requirement 
(coupled with a 
ment for circulation of fluids 
Rankine compresser) 
Sensible to latent 
Waste or solar heat 
As above, increased 
heat converter 
actuated power 
utilization of heat 
(coupled with a 
generation source, improved seasonal 
Rankine turbine adaptation and performance 
or reciprocating 
converter) 
__________________________________________________________________________ 
Referring to FIG. 6, a perspective drawing shows a machine in accordance 
with the present invention performing the variable effect process and 
using a rotating heat exchanger. The system is enclosed within a generally 
cylindrical outer tank having cylindrical side walls 44 closed by 
generally planar or slightly domed end walls 46 and 48. Within the 
stationary tank are rotatable cyclindrical drum members 50 and 52, 
connected, respectively, by support plates 54 and 56 to the rotating drive 
shaft 60 to produce rotation of the drums 50 and 52. The support plates 54 
and 56 double as vapor impermeable dividing walls to separate the drums 
into two separate processing compartments each holding liquids by virtue 
of ring flanges 50a, 50 b, and 52a and 52b which permit liquids to 
accumulate in pools in the lowest porton of the drums due to gravitational 
effect. Rotation of the drums causes the liquids from said pools to be 
moved in thin layers around the internal surface of the drums. Wipers 49 
and 51 are correspondingly located wipers with respect to each compartment 
are provided for controlling the thickness of these layers. At their 
internal ends, the drums are sealed from the chamber surrounding the drums 
in the cylindrical tank by sealing walls 62 and 64 and suitable seals 62a 
and 64a. A further vapor seal 60a prevents vapor leakage from or outer air 
leakage into the machine. 
Within the output side of drum 50 between supported plate 54 and ring 
flange 50a is a pool 66 of a heating circulant supplied from a piped 
source 68 by means of a pump 70 and, in turn, removed from the pool by a 
line 72. Similarly, between the support plate 56 and the ring flange 52b, 
there is a pool of cooling circulant 74 supplied through line 76 and 
withdrawn from the pool by line 78 by virtue of pump 80. The principal 
processing solution of the system is supplied through line 82 to a 
generator pool or chamber 32' in the bottom of tank cylindrical walls 44 
between end wall 46 and sealing wall 62 from which it is withdrawn by line 
84 which is provided with fins 86 and which terminates in the resorber 
pool 34' within the section of rotating drum 50 defined by wall 54 and 
ring flange 50b constituting the resorber 34'. Liquid is removed from the 
resorber 34' through line 88 to heat exchanger 90 which allows heat 
exchange with the fluid passing into line 82. Thereafter the heat 
exchanger fluid from the resorber 34' passes by valve 94 into absorber 
chamber 36' at the bottom of the tank cylindrical walls 44 between seal 
wall 64 and end wall 48. Fluid is removed from the absorber 36' through 
line 96 having fins 98 and extending around and into the rotating drum 52, 
specifically into the regenerator pool 40', between the support plate 56 
and the ring wall 52a. 
Finally, fluid is removed from the regenerator 40' through line 100 by 
means of pump 102 which acts as a system circulator to move the fluid once 
again through heat exchanger 90 and back into line 82. 
In the top of the cylindrical walls 44 of the tank above the rotating drums 
50 and 52 are trays 104 and 106. Tray 104 is in the compartment between 
sealing wall 62 and end wall 46 and tray 106 is in the compartment between 
sealing wall 64 and end wall 48. Tray 104 is designed to contain liquid 
which is condensed by coil 108 the structure together providing condensor 
38'. Coil 108 receives cooling circulant from supply line 110 and the 
warmed circulant passes out through line 112. 
Tray 106 also provides a pool and a sprayer such as perforated pipe 116 
which together with heating element 118 constitutes evaporator 42'. The 
heating element is, for example, a finned tube array containing heating 
circulant supplied through line 120 and exhausted through line 122. The 
sprayer is supplied with refrigerant condensed in 38' after throttling to 
the lower pressure by the valve in line 114. 
The off-center shaft 60 supports the two heat exchanger drums 50 and 52 and 
the drums are rotated and continuously wetted inside by solutions or 
circulants on both sides of the support walls 54 and 56. FIG. 6a shows 
wiper 49 on the outside surface and wiper 51 on the inside surface of the 
drum 50. These and correspondingly positioned wipers on drum 52 are fixed 
to the stationary frames and specifically to end walls 46, 48, or sealing 
walls 62 and 64. These wipers control the thicknesses of the solutions for 
optimal heat transfer. The inside of the drum contains the intermediate 
pressure stage, and seals 62a and 64a are provided against vapor leakage 
from the generator or to the absorber. 
FIGS. 6 and 7 constitute one arrangement of pressure vessels and heat 
exchangers provided for the process of FIG. 2. Station numbers shown on 
FIG. 7 correspond to those for the ideal fluid cycle of FIG. 3. Solution 
at the highest system pressure flows from the solution heat exchanger 90 
into the generator 32' at state 1. Heat for boiling the generator solution 
is first provided by resorber solution from pool 34' counterflowing in a 
thin film on the opposite side of the heat exchanger drum between support 
plate 54 and flange 50b and subsequently by the counterflowing heating 
circulant inside the drum surface between plate 54 and flange 50a and by 
generator solution returning to the resorber in finned line 84. The drum 
50 also permits heat exchange with superheated vapor on its way to the 
condenser 38'. Solution exits the generator 32' at state 2, is throttled 
to the intermediate pressure, sensibly cooled by counterflow with 
generator solution in finned line 84 and enters the resorber pool 34' at 
state 3. The solution piping 84 extends from the generator 32' to the 
resorber pool 34' around the rotating drum and through the stationary 
seal. In the resorber pool 34' vapor (from regeneration) is condensed in 
the solution on the internal drum surface, and solution exits the resorber 
34' at state 4. It is sensibly cooled in the heat exchanger 90, throttled 
to the lowest pressure in line 94, and enters the absorber 36' at state 5. 
In the absorber 36' vapor from the evaporator is condensed in the 
solution. The absorber heat is partially rejected to solution in 
regenerator 40' counterflowing in a thin film on the opposite side of the 
heat exchanger drum between plate 56 and flange 52a; the balance of the 
absorber heat is rejected to the counterflowing cooling circulant inside 
the drum between plate 56 and flange 52b, to the absorber solution 
returning to the regenerator 40' in finned line 96, and to vapor subcooled 
relative to the absorbing solution exiting the evaporator 42'. Solution 
exits the absorber 36' at state 6, is pumped to the intermediate pressure, 
is sensibly heated by counterflow with absorber solution in finned line 
96, and enters the regenerator 40' at state 7. In the regenerator 40' heat 
for boiling is provided by the absorber 36' and the vapor is conducted to 
the resorber 34'. The solution exits the regenerator 40' at state 8, is 
pumped to the highest pressure, and is sensibly heated in the solution 
heat exchanger 90, to state 1, thus completing the solution cycle. The 
condenser 38' and evaporator 42' are cooled and heated in a conventional 
manner. 
Heat transfer between the absorbent solution and the sensible heating and 
cooling circulants and internal heat transfer between solutions in the 
different pressure stages occurs across the rotating drum. There are four 
advantages for this design compared to a design using the more usual 
stationary heat exchangers. First, because solution layer thicknesses 
control permits higher heat and mass transfer rates. Second, the internal 
heat exchanger approach penalty is minimized by this design. Because the 
effective heat capacity flow rate of the absorbent solutions (Btu/hr 
.degree.F.) varies with concentration, a stationary heat exchange design 
with an intermediate sensible circulant would incur two pinch effect 
penalties with an intermediate sensible circulant. Third, the intermediate 
circulant loop and controls which the stationary design would require are 
not needed with the rotating design. Fourth, the drum is more easily 
mass-fabricated and the machine more easily assembled than would be the 
case if the usual state-of-the-art stationary tube or plate bundles were 
used. 
The drum surface is illustrated as a smooth cylinder for clarity. It may 
also be corrugated or finned in various ways. There are two major design 
considerations which determine if corrugation is desirable and to what 
extent; the total surface area of the drum is proportional to its heat 
exchanging capacity, and the cross sectional area of the drum is 
proportional to its vapor handling capacity. For large capacity machines, 
and especially if high pressure fluids such as water-ammonia are used, 
corrugation is desirable in order to reduce the length and diameter of the 
drum. Heat losses to ambient and the costs of fabrication and handling are 
thereby also reduced. The relative lengths of the several sections of drum 
as illustrated by FIGS. 6 and 7 may vary widely for different 
applications. For some applications the drum need not be extended to 
include the heating and cooling circulants. Conventional stationary pot 
boilers or spray equipment may be used for these sections of the 
generation and absorption subprocesses not involving internal heat 
transfer. 
FIGS. 6 and 7 do not show accumulators, bleed lines, purge for 
non-condensibles, or controls. The form of the evaporator and condenser 
heat exchangers, vapor precooler, solution heat exchangers, seals and 
bearings, and the piping and other component layout have been shown 
schematically for clarity. It will be understood that conventional known 
hardware can be used in these functions. It will also be apparent that the 
hardware can be employed, as noted above, with other processes. Either the 
variable effect or the other processes can use a machine having only a 
single drum. 
The process of FIG. 4 can be accommodated by a machine similar to that of 
FIGS. 6 and 7, using a second rotating heat exchanger drum or additional 
sections of a single drum for the evaporator and condenser. Arrangements 
for interconnection using the rotating heat exchanger drum with other two 
fluid variable effect processes or with Rankine converters will be easily 
discernable to one skilled in the art with the aid of FIGS. 6 and 7. 
A special arrangement for desalination is the machine of FIGS. 6 and 7 with 
the evaporator and condenser replaced by a common heat exchange surface. 
Ocean water may be throttled through a turbine into the low pressure 
evaporator side, sprayed on the common surface, and pumped out using shaft 
power from the throttling turbine. Product condensate which forms on the 
other side of the surface is also pumped out. For this application a large 
capacity corrugated drum, a much smaller capacity spray absorber, and a 
much smaller capacity pot boiling generator would be used. A particular 
advantage of the variable effect process for desalination is that the 
seawater is not substantially heated above its inlet temperature, so that 
scaling and corrosion, which plague most thermally actuated desalinators, 
do not occur. A second advantage is that only three pressure stages are 
required, in contrast to the dozen or more stages required with 
conventional thermal desalination processes achieving the same level of 
performance. 
FIGS. 8A through 8C are schematic diagrams which illustrate certain 
modifications to the FIGS. 6 and 7 heat pump/chiller machine to adapt it 
for other specific purposes. FIG. 8A shows a FIG. 7 machine modified for 
temperature amplifying. The structure physically looks much the same as 
FIG. 7 and therefore the corresponding parts have been given similar 
number designators with the addition of a "1" prefix to the number used in 
FIG. 7 where those numbers correspond. The locations of the heating and 
cooling circulants, generator, absorber, regenerator and resorber are the 
same. The absorber and evaporator operate at a higher pressure and 
temperature than the generator and condenser, the opposite of the FIG. 7 
heat pump, and all flow directions of absorbent solution are reversed. For 
example, it will be observed that the direction of flow in lines 168 and 
172 have been reversed. This is true also of the direction of flow in the 
heating circulant pool 166. A further observation shows that the 
corresponding thing is true in lines 176 and 178 with cooling circulant 
pool 164. The reversal of flow which has taken place is also indicated by 
the thermal cycle state numbers which have been rearranged. The pumps and 
valves have been moved to the generator end of the machine as much as 
possible because the generator operates at lower temperatures than the 
absorber, in contrast to the FIG. 7 heat pump for which the opposite is 
true. For example, pumps 1102 and 197 and valve 194 have been moved. 
Because of the pressure reversal, a pump is added to line 114 to replace 
the throttling valve of FIG. 7 between the condenser and evaporator. 
Slight modifications to the piping of FIG. 7 are made in FIG. 8A to 
prevent cavitation of pumps when moving fluid from low to higher pressure. 
A vapor precooler for the FIG. 8A machine is located at the condenser just 
after the pump for better performance, rather than a liquid precooler at 
the evaporator, as for the FIG. 7 machine. Spray line 16 runs directly 
across the top of the evaporator without a precooler. 
FIG. 8B shows a FIG. 7 machine modified as a sensible/latent heat converter 
for power generation or for improved performance of electrical heat pumps. 
Especially for the former purpose, a large capacity requirement and high 
pressure fluid such as ammonia-water or R-22 and organic amides, is 
anticipated, so that corrugated heat exchange drums 250, 252 are employed; 
this need not be done for smaller machines. Again, number designators 
corresponding to those used in FIG. 7 are provided with the addition of a 
prefix "2". Piping and absorbent flow directions for power generation are 
the same as those of the FIG. 7 machine. Fins (not shown) could be added 
to the outside surface of the corrugated drum to enhance heat transfer 
between the vapors and the drum for improved performance. Wipers are 
advantageously employed but must be suitably modified to conform to the 
corrugated shape. Use of fins would be especially desirable if an organic 
fluid, such as R-22 and hexyldiamide, were used, since such materials have 
high vapor sensible heat capacities. In view of the different function, 
evaporator and condenser structure is omitted, and the Rankine converter 
is substituted. 
The added Rankine converter 210 may be a turbine or reciprocating converter 
for power generation. For electric heat pump improvement the Rankine 
converter would be a rotary or reciprocating compressor and all flow 
directions would be the reverse of those shown by FIG. 8B, i.e., similar 
to those of FIG. 8A. 
If the heat pump of FIG. 8B were intended for industrial waste heat 
upgrading, changes in pump and valve location similar to those made for 
the temperature amplifier of FIG. 8A would be appropriate. Vapor duct 
design and converter support structure and location would vary depending 
upon the converter type and size and upon the fluid used. 
As has been mentioned, freedom to use different fluids in the variable 
effect subcycle and Rankine subcycle may be obtained by using coupled 
variable effect condenser-Rankine evaporator and variable effect 
evaporator-Rankine condenser heat exchangers. This can provide optimized 
performance for each subcycle and increased flexibility of mechanical 
design in return for heat exchange performance and cost penalties. For 
this approach, power generation or electric heat pump improvement would be 
obtained using the previously discussed machines, respectively, the heat 
pump/chiller of FIG. 7 or the temperature amplifier of FIG. 8A, with 
modified evaporator and condenser. 
FIG. 8C shows a FIG. 7 type machine adapted for desalination. In this case, 
parts corresponding to those in FIG. 7 are provided with the same number 
designators having a 3 prefix. Again, large capacity is assumed, so that 
corrugated drums 350, 352 are used. Almost all of the heat exchange within 
the machine is either to the regenerator 340 or from the resorber 334 
because the pressure difference between the evaporator 344 and condenser 
338 will be small, determined by their heat exchange approach temperature 
difference. The temperature ranges of operation for those sections of the 
generator and absorber exchanging heat with the external circulants will 
be small also. Thus, heating circulant chamber 66 and cooling circulant 
chamber 74 are omitted and each drum 350, 352 provides only one chamber. 
Therefore, a pot boiler 377 and conventional spray absorber 335 are 
cost-effective choices for the external heat exchange compared to using 
the drum for both internal and external heat exchange. Regeneration 
chamber 340 is then defined by drum 350 with wall 354 and ring flange 350b 
and resorber chamber 334 is defined by drum 352 within wall 356 and flange 
352a, with the two chambers being open to one another for free vapor 
exchange at middle pressures. Sprayer 335 acts on coil 371 connected by 
lines 337a 337b to lines 368 and 372 which supply the cooling circulant. 
Pump 335b recirculates solution from the absorber pool through line 368 to 
the sprayer. Boiler coil 377 is supplied with heating circulant by lines 
376 and 378. 
Because of the small pressure difference, the coolest end of the resorber 
334 and hottest end of the regenerator 340 are very nearly at the same 
temperature, so that the solution heat exchanger of FIG. 7 may be 
eliminated. Line 382 is connected to line 3100 via pump 3102 and 388 is 
connected through valve 394 without the heat exchanger. If efficiency were 
of paramount importance, the solution heat exchanger could be used. Fins, 
not shown, could be used on both drums sections to enhance sensible heat 
recovery from vapors. The evaporator 342 and condenser 338 have a single 
heat exchange surface 305 augmented with fins 3118 and 3108, so that all 
of the heat needed for the former is supplied by the latter. This does not 
permit an exact mass balance between the condenser and evaporator flows 
because the enthalpies of vaporization of seawater and pure product water 
differ slightly. Since the rates of water condensed and evaporated must be 
equal for steady state operation of the machine, a small bleed line from 
the condenser to the evaporator and controls for the seawater and product 
water pumps, not shown, would be required. A condenser vent 339 is shown 
which permits vapor flow to the condenser from the generator; a slightly 
sloping tray below the vent holds product water to one side for removal by 
pump 328. A turbine-pump combination is shown by FIG. 8c for the recovery 
of work generated by turbine 320 throttling seawater at atmospheric 
pressure down to the low operating pressure of the absorber. This work 
plus additional auxiliary work input, not shown, would be used via shaft 
320a to pump exhausted (concentrated in salt) seawater in the evaporator 
and product in the condenser from the low pressures inside the machine 
back to atmospheric pressure with pumps 322 and 328. Other arrangements 
for the turbine-pump and connections with auxiliary power could be 
provided. 
FIGS. 7, 8A, 8B and 8C represent preferred embodiments of rotating drum 
members, some of which have circumferential surface extension. These 
embodiments represent horizontally-rotated, drum-type, and counterflow 
heat exchangers for use in absorption machines. As a further feature the 
heat exchanger preferably employs two axially counterflowing fluids, at 
least one of which is an absorption fluid, as known in the prior art, and 
which changes in concentration and temperature concurrently with 
evaporation or condensation of the volatile absorption fluid component at 
a constant pressure. 
The rotating drum means is preferably compactly extended circumferentially, 
for example, with circular or helical corrugations or with circular or 
helical fins. These circumferential extensions segment the axial fluid 
flows into many small volumes isolated from each other. The drum means is 
held generally horizontally to permit the axial counterflow of the two 
fluids as films over its interior and exterior surfaces. One or both of 
these films is exposed to a vapor volume containing the volatile 
absorption fluid component at constant pressure. The vapor volume is 
either within the interior of the drum or within the volume between the 
outside surface of the drum and a surrounding housing, or both of these, 
if two absorption fluids are used. The rotating drum interior access means 
for liquid, or for liquid and vapor, and sealing means for isolating the 
interior vapor volume may be provided. Rotation permits renewal of 
vapor-equilibrated absorption fluid film with fresh fluid from a gravity 
pool inside or outside of the drum, or in both locations. Bearing means 
for mechanical support of the rotating drum are provided. The gravity pool 
is either the volume between the extensions of the interior drum surface 
at its bottom or low side or the volume between the extensions of the 
exterior drum surface and a surrounding housing, or both of these. 
Means for rotating the drum may, for example, include a coaxial shaft or 
either a hermetically sealed motor inside the shell or a magnetically 
coupled motor exterior to the shell, which features are known in the art 
and may be optionally used with this invention. 
FIGS. 9a through 9l are illustrations of various corrugation and fin styles 
and combinations of styles which are readily produced by various methods 
well known in the art and advantageously employed for the horizontal 
rotating heat exchanger and mass transfer drums used in the FIGS. 6 
through 8C machines or other absorption machines. FIGS. 9a and 9b are, 
respectively, cross sections of drums with corrugations producible by 
hydraulic forming and helical corrugations producible by rolling. Circular 
corrugations have an advantage in that they can be made deeper than 
helical corrugations. Helical corrugations have an advantage in that fluid 
is axially screw conveyed by the drum rotation, as well known in the art, 
which permits higher relative fluid velocities at the surface with fluid 
pumped in opposition to the screw conveyance. Fluid on the opposite side 
would have a lower velocity with helical than with circular corrugations. 
Hence, the helical style lends itself best for use with an absorption 
fluid on one side and a sensible circulant on the other. FIGS. 9c and 9d 
are, respectively, cross sections of drums with circular fins producible 
by press-fitting and helical fins producible by press-fitting of an 
internal fin or continuous welding of an external fin. As is true for 
corrugations, the helical style fin is most appropriate for use with one 
absorption fluid and one sensible fluid. Both the circular and helical 
fins have the advantage compared to corrugations of different spacing 
inside and outside the drum for machines efficient to the heat transfer 
requirements of the two fluids. FIGS. 9e and 9f are, respectively, a cross 
section and an end view of a drum with interior circular fins and exterior 
longitudinal fins. The longitudinal fins lend themselves well for use with 
air or exhaust gas, and the circular fins with an absorption fluid. 
Longitudinal fins are producible by continuous welding or by extrusion. 
FIGS. 9g and 9h are, respectively, a cross section and an end view of a 
drum with interior helical fins and exterior longitudinal fins. The same 
advantages for particular uses are obtained as is true with longitudinal 
and helical fins in the earlier examples. FIG. 9l is an end view of a drum 
with interior longitudinal fins and exterior circular or helical fins, 
again obtaining the advantages of these styles as already described. FIGS. 
9i, 9j and 9k are cross sections of helically corrugated drums including, 
respectively, interior helical fins, exterior helical fins, and both 
interior and exterior helical fins. The combinations are producible by 
threading the fins onto the corrugations. These combinations permit more 
compact heat exchangers than obtainable with helical corrugations alone. 
It will be apparent to one skilled in the art that other combinations of 
fins and corrugations can be produced which are suitable for various 
combinations of absorption and sensible or Rankine fluids. 
FIG. 10 is a cross sectional view of a circumferential surface extended, 
horizontally-rotated, and counterflow heat exchanger drum and vapor 
absorbing or releasing device for use in absorption machines similar to 
those in FIGS. 7, 8A, 8B and 8C. Numbers corresponding to those used in 
FIG. 7 are employed to designate similar parts but with the addition of a 
prefix 4. Thus, the housing or outer tank has its cylindrical walls 
designated 444 and the end wall 448 is the only one seen in this partial 
view. The rotating drum is 452. In the FIG. 10 embodiment, one of two 
axially counterflowing fluids is an absorption fluid 400 which changes in 
concentration and temperature concurrently with evaporation or 
condensation of the volatile absorption fluid component at a constant 
pressure. The second fluid 401 is a sensible circulant. The use with an 
absorption fluid and a sensible fluid is contemplated in FIGS. 6 through 
8C. Embodiments with two absorption fluids have also been described 
generally in the discussion of FIGS. 6 through 8C and combinations of an 
absorption fluid and a Rankine fluid have been mentioned above. In this 
embodiment, both liquid and vapor phases of the fluids inside and outside 
of the drum 452 are isolated from one another. 
The drum 452 is compactly extended with both inwardly extending circular 
fins 451 and outwardly extending circular fins 453. Other fin or 
corrugation styles, e.g., those illustrated in FIGS. 9a through 9l, may be 
employed alternatively. These circumferential extensions segment the axial 
fluid flows into many small volumes each isolated from the other, and 
inhibit unwanted fluid volume mixing. The drum 452 has both ends closed, 
one by flange 452a and stationary bushing 455 through which extends hollow 
drive shaft 460, with bearings between the bushing and each rotating 
member. The other end of drum 452 is closed by wall 457 which supports 
stub drive shaft 461 in turn rotatably supported by bearing block 463 in 
housing wall 464. The drum 452 is held approximately horizontally to 
permit the axial counterflow of the two fluids as films over its interior 
and exterior surfaces. The closed ends of the drum isolate both liquids 
and vapors inside and outside of the drum from one another. Pool 400 
collects by gravity in the bottom of housing wall 444 to supply the film 
on the outside surface of drum 452 and pool 401 collects by gravity in the 
bottom of the inside of the drum 452 to supply the film on the inside 
surface of drum 452. One of these films, for example on the outside of 
drum 452, is exposed to a vapor volume containing the volatile component 
of the absorption fluid at constant pressure. The interior volume may be 
used in other embodiments, and both volumes contain the volatile component 
of the fluid, if two absorption fluids are used. Drum interior access for 
liquid, or for liquid and vapor, and sealing means for isolating the 
interior vapor volume are provided through bushing 455 and hollow shaft 
460. In FIG. 10 these are the circulant outlet pipe 478 which passes 
through the shaft and the housing end wall 448 and the inlet pipe 476 
which passes through the bushing 455 and a stationary seal in the housing 
end wall 448. Rotation permits renewal of the vapor-equilibrated 
absorption fluid film with fresh fluid from gravity pools 400 and 401. 
Cylindrical bearings for hollow shaft 460 are supported on support segment 
459 in turn affixed to housing wall 444. 
FIG. 10 also shows means for rotating the drum without providing a rotating 
seal through the housing using magnetic coupling means. For example, a 
motor shaft 457 of a driving motor (not shown) coaxial with the axis of 
drum rotation may be terminated in a circular magnetic piece 457a 
providing a coupling pole face. Inside the housing a similar circular 
magnetic pole piece 460a is fixed to hollow shaft 460. Close positioning 
of pole pieces 460a and 457a enable magnetic coupling through non-magnetic 
wall 448 to the motor to drive the central hollow shaft 460. Shaft 460, in 
turn, drives drum 452 to which it is attached at the drum inner wall by 
support spokes 456. Other means, such as a hermetically sealed motor, or 
an internal liquid or vapor turbine could be used instead. 
Any of the FIG. 7 through FIG. 8C machines or others could be designed as 
modules of larger machines in which the modules could be served by common 
pumps and throttling valves selected to permit variable flow rates which 
might be desired for capacity control. Such variable valves and pumps 
could be used on single modules also, but less cost-effectively. Large 
capacity heat pumping, temperature amplifying, power producing, or 
desalinating applications would benefit from such modularity by the 
increased flexibility of operation and standardization of manufacture 
which modularity typically provides. 
The present invention has been described in terms of broad process concepts 
and functional blocks representative of machinery or systems. A specific 
example of one preferred form of a single fluid loop variable effect 
machine has been illustrated and described. Modifications to each of the 
illustrated and described processes and to the machine have been 
described. Further modifications appropriate to the applications listed in 
Table 1, or others, will occur to those skilled in the art. All such 
modifications within the scope of the appended claims are intended to be 
within the scope and spirit of the present invention.