Ice harvesting/water chiller machine

An ice harvesting/water chiller machine with an improved evaporator assembly having a plurality of plate-type heat exchangers oriented vertically in face-to-face parallel relation. A water reservoir is located above the heat exchangers. Water is distributed from the reservoir downwardly to flow over the outside surfaces of the heat exchangers to effect a substantially even distribution of water over the outside surfaces as it flows downwardly thereover. Cold refrigerant is distributed to the tops of the heat exchangers to cascade downwardly over the inside surfaces of the heat exchangers to effect a substantially even distribution of refrigerant over the inside surfaces as it cascades downwardly thereover. A cold refrigerant feed tube extends across the top of each heat exchanger substantially the entire width thereof. The tube has spaced openings along the tube over substantially the entire width of the heat exchanger which openings communicate with the interior of the heat exchanger. The tube receives cold refrigerant and distributes it through the openings into the interior of the heat exchanger to cascade downwardly over the inside surfaces thereof.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to an ice harvesting/water chiller machine of the 
type for producing large quantities of ice and/or chilled water and where 
the ice may be used for thermal energy storage for cooling. 
Thermal energy storage has been used for many years. In the past it was 
economically feasible with certain classic cooling applications such as 
churches, theatres, and dairies to utilize the stored cooling effect of 
small refrigeration systems operated over long periods of time to meet 
large cooling requirements of short duration. In more recent years, 
thermal energy storage has been used to take advantage of utility pricing 
policies. Utilities have instituted time-of-use rate schedules to 
encourage the shifting of electrical demand to off-peak, low electrical 
demand periods of the day, periods during which utilities have excess 
generating capacity. Large cooling requirements are prime candidates for 
electrical load shifting of this type. By shifting electrical demand to 
off-peak hours, it is possible to obtain cooling during peak hours at 
close to off-peak costs. 
Hence, as with other ice harvesting machines, the ice harvesting machine of 
the present invention is used to produce large quantities of ice during 
off-peak periods when the cost of electricity is relatively low, and store 
the ice for cooling during peak periods when the cost of electricity is 
relatively high, thus avoiding use of large amounts of electricity during 
high cost periods. 
Ice harvesting machines are known in the art. U.S. Pat. Nos. 4,622,832, 
4,531,380, and 2,113,359 disclose such machines where cold refrigerant is 
distributed over the outer surfaces of vertical tubes, and ice is formed 
on the inside of the tubes. Other patents disclose such machines using 
vertical plate-type heat exchangers for forming the ice. Examples are U.S. 
Pat. Nos. 4,044,568, 3,566,896 and 2,448,453. U.S. Pat. No. 3,546,896 
discloses a "pillowed" plate-type heat exchanger where refrigerant is fed 
within the heat exchanger and water flows from an upper reservoir down 
over the outer surfaces. 
The ice harvesting/water chiller machine of the present invention 
represents an improvement over such prior machines in providing a machine 
that is exceptionally efficient for producing large quantities of ice 
and/or chilled water utilizing an improved evaporator assembly. 
Generally, the machine of the present invention includes a storage tank for 
collecting and storing ice or chilled water produced by the machine for 
use such as in room cooling during peak load hours, and a refrigeration 
system for producing the ice and depositing it into the storage tank. The 
refrigeration system includes an improved evaporator assembly having a 
plurality of plate-type heat exchangers oriented vertically in 
face-to-face, parallel, relation above the tank. Each heat exchanger is of 
the "pillowed" type formed from multiple plates spot welded together at 
locations spaced uniformly over substantially the entire heat exchanger. 
The heat exchanger is then inflated so as to pillow between the spot welds 
to form interior passages between the plates for the flow of refrigerant 
therethrough. 
The assembly further generally includes a water reservoir above the heat 
exchangers. Water is distributed from the reservoir downwardly to flow 
over the outside surfaces of the heat exchangers to effect a substantially 
even distribution of water over the outside surfaces as it flows 
downwardly thereover. Cold refrigerant is distributed to the tops of the 
heat exchangers and cascades downwardly over the inside surfaces through 
the pillowed passages to effect a substantially even distribution of 
refrigerant over the inside surfaces as it cascades downwardly thereover. 
To provide such distribution a tube extends across the top of each heat 
exchanger. The tube has spaced openings along the tube over substantially 
the entire width of the heat exchanger. These openings communicate with 
the interior of the heat exchanger. Cold refrigerant is fed through the 
tube and distributed through the openings into the interior passages of 
the heat exchanger and cascades downwardly over the inside surfaces 
thereof, thus cooling the water as it flows downwardly over the outer 
surfaces. 
After a build up of ice of a predetermined thickness on the outer surfaces 
of the heat exchangers, hot gas is cycled into the interior passages to 
release the ice which falls into the storage tank below. 
The improved evaporator assembly of the present invention produces an 
exceptionally uniform build up of ice over substantially the entire outer 
surfaces of each heat exchanger, and does so at high efficiency due to the 
uniform flow of both cold refrigerant and water over the heat exchanger 
surfaces.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
An ice harvesting/water chiller machine of the present invention is 
generally shown by the block diagram of FIG. 1. The machine 10 includes a 
water/ice energy storage tank 12 into which ice produced by the machine is 
deposited for storage and later use during off-peak power periods such as 
for producing chilled water or for room cooling. Above the tank is an 
evaporator assembly 14 which is comprised of a plurality of evaporator 
modules 16. Each module includes an upper water reservoir 18 and a 
plurality of plate-type heat exchangers 20. 
The evaporator assembly is actually part of a refrigeration system 22 which 
has conventional components such as compressor, condenser, high side 
float, low pressure receiver, valves, and associated components, and 
therefor will not be described. 
The machine further includes a system controller 24 which may be of the 
solid state electronic, programmable type and which controls the operation 
of various valves 26, 28 and 30. The valve 26 is in a feed line 32 and 
controls the flow of hot gas refrigerant to the evaporator assembly. The 
valve 28 is in a feed line 34 and controls the flow of cold refrigerant to 
the evaporator assembly The valve 30 is in a feed line 36 and controls the 
flow of refrigerant from the evaporator assembly. 
The machine also includes feed lines 40, 42, and 44, and pumps 46 and 48 
which are part of a chilled water system 50. Hence, chilled water from the 
storage tank 12 may be pumped by way Of pump 46 and feed line 40 for use 
in the chilled water system, and also may be fed from the chilled water 
system by way of feed line 44, or pumped from the storage tank by way of 
pump 48 and feed line 42 to the reservoirs 18 by way of a valve 52 and 
feed lines 54 for use in producing ice. 
The evaporator assembly 14 of the present invention will be more fully 
described with reference to figures 2-10. The assembly has a supporting 
frame 60 for supporting the various components of the assembly. The 
evaporator modules 16 are supported across the length of the frame. Each 
plate-type heat exchanger 20 is of the "pillowed" type as described in 
U.S. Pat. No. 3,458,917, and hence is formed of at least 2 plates 62 and 
64 (FIG. 9) spot welded together by spot welds 66 which are spaced 
uniformly over the entire heat exchanger. The edges of the sheets have 
seam welds to fully seal the perimeter of the heat exchanger except for 
the inlets and outlets as will be described. After the sheets are welded 
together, the heat exchanger is inflated causing the sheets to pillow 
between the welds thus producing internal passages for the flow of 
refrigerant therethrough. 
Just beneath the seam weld that extends along the top edge of each heat 
exchanger is a pillowed region 70 where there is an absence of spot welds. 
A tube 72 extends within the region 70 at the top of the heat exchanger 
substantially the entire width of the heat exchanger, and further extends 
outwardly from the heat exchanger through an opening 74 in the edge of the 
heat exchanger near the top seam. Within the region 70 the tube 72 has 
openings 76 in the wall of the tube. The openings face upwardly and are 
spaced along substantially the entire portion of the tube within the heat 
exchanger. By way of example, the tube 72 may be 1/4 inch O.D. and the 
openings 76 may be 3/64 inch in diameter and spaced at approximately two 
inch intervals. The end of the tube 72 outside of the heat exchanger is 
connected through appropriate plumbing 80 and 34, and a valve 28 to the 
refrigeration system 22. 
The purpose of the tubes 72 and associated valves and plumbing is to 
deliver cold refrigerant to the interior passages of the heat exchangers 
during the refrigeration cycle. After a predetermined accumulation of ice 
on the outer surfaces of the plates 62 and 64 of each heat exchanger the 
system controller 24 controls the various valves to interrupt the feeding 
of cold refrigerant through the tube 72 into the heat exchangers, and 
instead delivers hot gas refrigerant to the interior passages of the heat 
exchangers to release the ice from the outside surfaces and allow it to 
fall into the storage tank. This hot gas is delivered to each heat 
exchanger by way of a sleeve or tube 82 that extends outwardly from the 
inlet opening 74 and is suitably secured such as by welding at the inlet 
to seal the opening. The sleeve 82 surrounds the tube 72 to define 
therebetween an annular chamber 84. A T-fitting 86 is secured to the end 
of the sleeve and is connected by feed lines 88 and 32, and a valve 26 to 
the refrigeration system 22. The end of the sleeve has a cap 90 with a 
central opening 92 through which the tube 72 extends. The tube 72 is 
suitably secured in the opening 92 such as by a weld to seal the chamber 
84. Hence, the chamber 84 communicates with the interior passages of the 
heat exchanger as do the openings 76 in the tube 72. 
A tube 100 covers the top edge of the heat exchanger and presents an upper 
rounded surface 102. The tube 100 may be plastic and may have a slit 104 
in the tube wall along its entire length. The tube is placed over the 
upper edge of the heat exchanger with the upper edge extending through the 
slit 104. As will be further explained, the upper rounded surface 102 of 
the tube acts to distribute the flow of water evenly to both sides of the 
heat exchanger. Each heat exchanger also has hangers 110 which may be in 
the form of stub pipes extending outwardly from the side edges of the heat 
exchanger. Each heat exchanger is in effect hung on the frame with the 
hangers 110 resting on frame members 112. Each heat exchanger is secured 
in position by suitably attaching it to appropriate frame members. 
A refrigerant outlet 120 is located at a side edge near the bottom of each 
heat exchanger. The outlet is connected by feed pipes 122 and 36, and a 
valve 30 to the refrigeration system 22. A bypass line 124 removes liquid 
refrigerant from the heat exchanger during the harvest (defrost) cycle. 
The water reservoir 18 of each module is directly above the heat exchangers 
and includes a pan 130 suitably supported by the frame and a removable lid 
132. The bottom of the pan has rows 134 of holes 136. The rows are located 
directly above the upper edges of the heat exchanger and are vertically 
aligned with the longitudinal axes of the tubes 102. The holes in each row 
are spaced along substantially the entire width of the heat exchanger. 
Within each pan is a rectangular trough 140 spaced from the bottom of the 
pan and extending between the pan's side walls. The trough 140 has 
openings 144 spaced along substantially its entire length. The openings 
are located on both sides of the trough where its bottom wall and side 
walls meet. See FIGS. 5-7. A water feed pipe 148 is connected to a side 
wall of the trough at an intermediate location. The feed pipe 148 is 
connected to th feed lines 54 to receive water by way of the valve 52. 
Hence, water delivered through the feed pipes 54 and 148 to the troughs is 
distributed through the openings 144 across the widths of the pans. From 
there the water is distributed through the openings 136 in the bottoms of 
the pans and onto the upper rounded surfaces 102 at the tops of the heat 
exchangers. 
By way of operation, water delivered to the reservoirs is distributed 
through the holes in the bottoms of the reservoirs onto the rounded upper 
surfaces at the tops of the heat exchangers. From there the water flows 
over both sides of the rounded surfaces and evenly over the outer surfaces 
of the heat exchangers. During the refrigeration cycle cold refrigerant is 
fed through the tubes 72 and openings 76 into the interiors of the heat 
exchangers near the tops. From there the cold refrigerant cascades 
downwardly through the interior passages and over the interior surfaces of 
the heat exchangers. This, of course, freezes the water producing ice on 
the outer surfaces. The ice is allowed to build up to a prescribed 
thickness. By way of example that thickness may be approximately 5/16 
inch. When the ice builds to the prescribed thickness the system 
controller places the refrigeration system in a harvest (defrost) cycle 
interrupting the delivery of cold refrigerant to the heat exchangers and 
instead delivering hot gas refrigerant to the interior passages by way of 
the chambers 84. This releases the ice sheets from the exterior surfaces 
allowing them to fall into the storage tank below. 
The heat exchanger assembly of the present invention, particularly with the 
tubes 72 having the spaced openings 76 for the even distribution of cold 
refrigerant within the heat exchangers, provides high efficiency with 
simple construction and low cost. The result is the efficient production 
of ice with exceptionally uniform thickness over substantially the entire 
outer surfaces of the heat exchangers. By way of example, machines of the 
type to which this invention relates may produce over 300 tons of ice per 
day. 
There are various changes and modifications which may be made to the 
invention as would be apparent to those skilled in the art However, these 
changes or modifications are included in the teaching of the disclosure, 
and it is intended that the invention be limited only by the scope of the 
claims appended hereto.