Abstract:
In an absorption type chiller heater, a generator is heated in order to heat a refrigerant-mixed solution to generate refrigerant vapor. This heating is generally carried out by causing high-temperature combustion gas to flow in contact with heat transfer fins, which are provided on the periphery of the generator. The aforesaid burner uses a burner of liquid-fuel combustion structure to produce a longer flame as compared to that of a gas burner. The extremity of the lengthened flame coming into contact with the heat transfer fins can cause problems such that the fins are locally overheated to burn out. In this view, the present invention arranges a flame buffer plate between the liquid fuel burner and the heat transfer fins and provides a curved flame channel. This forms a curved flame, whereby the flame, despite of its great length, is kept from its extremity coming into contact with the heat transfer fins. Besides, the flame channel, even if long, is curved to prevent larger outer dimensions of the entire chiller heater.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ammonia absorption chiller heater with air-cooling means and a modification method therefor. 
     2. Description of the Related Art 
     An absorption chiller heater in Japanese Patent Laid-Open Publication No.Hei 11-223432 is publicly known which uses ammonia as a refrigerant and water as an absorbent and is equipped with air-cooling means. 
     Description will here be given of the known art mentioned above. 
     In a generator, ammonia aqueous solution is heated to generate ammonia vapor. 
     This heating is performed by using a gas burner. 
     The ammonia aqueous solution having ammonia vapor generated therefrom makes dilute ammonia water. 
     The ammonia vapor generated in the generator is introduced to a condenser. The vapor is circulated through a heat exchanger while air-cooled by a cooling fan, thereby being condensed into liquid ammonia. 
     The condensed liquid ammonia is let through an expansion valve for pressure reduction, and fed to an evaporator. 
     In the evaporator, the liquid ammonia evaporates into ammonia vapor, which consumes heat of evaporation to cool brine. This cooled brain is circulated through cool/heat loads to offer a refrigeration effect or cooling effect. 
     Meanwhile, the dilute ammonia water obtained through the generation of ammonia vapor in the generator described above is introduced through a pressure-reducing valve and sprayed into the upper part of an absorber. At the same time, the ammonia vapor having evaporated in the evaporator is also introduced to the absorber mentioned above. 
     In this absorber, the dilute ammonia water absorbs the ammonia vapor to make dense ammonia aqueous solution, which is sent back to the aforementioned generator by a solution pump. The ammonia aqueous solution is then reheated by the gas burner to generate ammonia vapor therefrom, making diluted ammonia water again. 
     Subsequently, these processes are repeated to carry out the refrigeration cycle. 
     As has been described above, the known art uses a gas burner to heat ammonia aqueous solution in the generator. 
     The use of a gas burner is advantageous for compact configuration of the entire absorption chiller heater. However, gaseous fuel is high in cost per calorie and therefore uneconomical as compared to liquid fuel. 
     Under such circumstances, conversion of the gas burner into a fuel oil burner is desired by users. 
     Liquid fuel is, however, greater in specific gravity and viscosity as compared to gaseous fuel. Therefore, liquid fuel needs to be atomized by spraying so as to mix with air, which elongates the flame. 
     Long flames from a burner give rise to a problem as follows: 
     The generator of an absorption chiller heater typically comprises heat transfer fins on its peripheries. Here, high-temperature gas produced by combustion flows in contact with the heat transfer fins to heat the entire generator. 
     If a flame reaches the heat transfer fins, the fins might locally be overheated until burned out, or combustion-produced solids might adhere to the fins to hamper the heat transfer. Thus, the burner must be placed so that the extremity of the flame cannot come to touch the heat transfer fins. 
     Accordingly, the longer the flame is, the greater the distance between the burner and the generator must be to establish a flame channel greater in length. This enlarges the entire shape and size of the absorption chiller beater. On this account, a wider floor space is required for installation. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a main object of the present invention is to provide a method of modifying a ready-made absorption chiller heater that is designed and fabricated to use a gas burner into an absorption chiller heater for use with a fuel oil burner, without increasing the entire shape of the chiller heater. 
     Another object of the present invention is to provide an “absorption chiller heater using a fuel oil burner” which is nearly equal in shape and size to an absorption chiller heater using a gas burner. 
     The objects stated above are, in other words, to improve absorption chiller heaters of conventional examples on condition that the heat transfer fins never be overheated to burn out and the combustion-produced solids never be deposited on the heat transfer fins to hamper the heat transfer. 
     The foregoing objects have been achieved by the provision of the present invention whose basic principle is as follows: 
     The lengthy flame from a fuel oil burner is directed toward a flame buffer plate (to put it more correctly, the flame buffer plate is opposed straight to the shooting direction of the flame from the fuel oil burner). The flame buffer plate is formed of refractory material. 
     This flame buffer plate preferably is a member moderate in width, having such shape and size that the flame (i.e., the flow of burning gas) can make a detour around the flame buffer plate. 
     In such configuration, a long flame ejected from the fuel oil burner collides against the flame buffer plate, changing its flowing direction to make a detour around the flame buffer plate toward the generator. This accordingly forms a curved flame. 
     The flame ejected from the fuel oil burner is indeed long but curved. Therefore, the flame channel, which is formed in conformity to the curved shape of the flame, also has a curved shape. 
     In spite of its greater length, the flame channel is curved and therefore relatively small in outer dimensions. This allows the absorption chiller heater including the flame channel to be compact in outer dimensions. 
     According to the present invention, “the distance between the generator and the nozzle of the liquid fuel burner” in an air-cooled absorption type chiller heater with a liquid fuel burner is generally equalized to “the distance between the nozzle of the gaseous fuel burner and the generator.” Besides, there is no danger of locally overheating the heat transfer fins of the generator or depositing combustion-produced solids thereon to hamper the heat transfer. 
     In addition, according to the present invention, air-cooled absorption type chiller heaters designed and fabricated to be equipped with a gas burner can be modified into air-cooled absorption type chiller heaters with a liquid fuel burner. The modification can be made without the danger of allowing flames to reach the heat transfer fins while suppressing increases in shape and size. 
     The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a general sectional view showing an embodiment of the air-cooled absorption type chiller heater of the present invention; 
     FIG. 2 is an exploded perspective view showing the essential parts of the embodiment of FIG. 1, taken along the plane Z—Z of FIG. 1; and 
     FIG. 3 is a perspective view showing the vicinity of what is shown in FIG. 2 with the casing removed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 shows an air-cooled ammonia absorption refrigerator, which is a modification example obtained by applying the present invention to a ready-made, air-cooled ammonia absorption type refrigerator equipped with a gas burner. 
     What is essential in the modification is to remove the gas burner and install a kerosene burner  8  instead. This modification involves the installation of the members shown on the right of the plane Z—Z and a kerosene burner cover  11   d.    
     An air-cooled ammonia absorption type chiller heater has both functions of cooling and heating. The cooling (or refrigeration) function is the same as that of the air-cooled ammonia absorption type refrigerator. 
     An air-cooled ammonia absorption type refrigerator uses ammonia as a refrigerant and water as an absorbent. The ammonia absorption type refrigerator of FIG. 1 is essentially comprised of the following component members: a generator  1 ; a gun type of liquid fuel burner (kerosene burner)  8 ; a condenser  3 ; an evaporator  4 ; an absorber  5 ; and piping for connecting these devices. The refrigerator also comprises a fan  6  for supplying the condenser  3  with cooling air (shown by the arrows b and c). This means that the refrigerator is of air-cooled type. 
     The generator  1  contains ammonia aqueous solution which is to be heated by high-temperature combustion gas produced by the kerosene burner  8 . To improve the efficiency of heat transfer in this heating, the generator  1  is provided with a number of heat transfer fins  1   a.    
     Ammonia vapor is generated from the heated ammonia aqueous solution, thereby making dilute ammonia water. The dilute ammonia water is high in ability to absorb ammonia vapor as compared to dense ammonia aqueous solution. 
     The ammonia vapor having evaporated in the generator  1  is introduced through piping  2  to the condenser  3 . Here, the vapor is cooled by cooling air (the arrows b and c) to condense into liquid ammonia. The heat of condensation emitted here is taken away by the cooling air (the arrows b and c) circulated by the fan  6 . 
     The liquid ammonia having condensed in the condenser  3  is sent through piping  7  and a pressure reducer  7   a  to the coiled piping in the evaporator  4 , whereby the liquid ammonia evaporates into ammonia vapor. 
     In evaporation, the liquid ammonia consumes the heat of evaporation to cool the brine (shown by the arrows f, g, and h) which flows in contact with the periphery of the aforementioned coiled piping. 
     Meanwhile, the dilute ammonia water having generated ammonia vapor in the generator  1  is introduced through piping  10  and a pressure reducer  10   a  to the absorber  5 . The ammonia vapor evaporated in the evaporator  4  is also introduced through piping  16  to the absorber  5 . 
     In the absorber  5 , the dilute ammonia water absorbs the ammonia vapor to make dense ammonia aqueous solution. 
     While the ammonia vapor in the absorber  5  is absorbed into the diluted ammonia water, the absorber  5  is cooled by the cooling air of the fan  6 . This decreases the pressure inside the absorber  5 . As a result, new ammonia vapor generated in the evaporator  4  continuously flows into the absorber  5 . 
     The dense ammonia aqueous solution created in the absorber  5  is let through piping  17  and is sent by a solution pump P 1  to the aforementioned generator  1 , whereby the solution is heated to generate ammonia vapor, making diluted ammonia water again. 
     The foregoing constitutes the refrigeration cycle which is continuously repeated to cool the brine in the evaporator  4 . The cooled brine is circulated and fed by a brine pump P 2  to e.g. fan coil units (not shown) provided in rooms, so as to fulfill the cooling function. 
     Now, description will be made on the configuration and function of the essential parts of the present invention. 
     Originally, on the right side of the plane Z—Z shown in FIG. 1 was mounted a gas burner. The gas burner had a number of nozzles in a planar arrangement so that the whole nozzles make a broad, short flame. 
     In the present invention, the above-mentioned gas burner is removed, and the kerosene burner  8  is mounted instead. 
     The modification by replacing a gas burner with the kerosene burner  8  as described above is applicable not only to ammonia absorption refrigerators but also to absorption type chiller heaters in general. 
     The above-mentioned modification can also be applied to existing absorption type chiller heaters. It is also applicable to unused, gas-burner-typed absorption type chiller heater. Moreover, the modification can be applied to semi-fabricated products which have been designed and fabricated to be equipped with a gas burner. 
     The aforementioned kerosene burner  8  has a flame nozzle which is generally horizontally directed to the heat transfer fins  1   a  of the generator  1 . The generator  1  has a longitudinal, cylindrical shape. The upper half of the generator  1  serves as a vapor-liquid separating space, and the lower half acts as a heat-receiving zone. The heat transfer fins  1   a  are mounted generally horizontally on the periphery of the heat-receiving zone. Accordingly, the generally horizontal installation of the kerosene burner  8  toward the heat transfer fins  1   a  allows the burner  8  to be installed at a lower position. 
     The lower installation position of the kerosene burner  8  shifts the center of gravity of the entire chiller heater downward for higher stability. In addition, the lower installation position is advantageous to provide a vertical flame buffer plate and a curved flame channel. 
     Between the above-described kerosene burner  8  and the generator  1  is provided a flame buffer plate  13  of refractory material, which is faced generally perpendicular to the shooting direction of the flame from the kerosene burner  8 . Thereby, the generally horizontal, lengthy flame ejected from the kerosene burner  8  collides against the flame buffer plate  13  mentioned above. Here, the collision forces the flame to make an upward detour. As shown in FIG. 1, a flame channel  14  is curved so as to introduce the flame to the upward detour. This forms a curved long flame  9  which will not reach the heat transfer fins  1   a.    
     In the present embodiment, the flame buffer plate  13  is fixed to the external wall  14   a  of the flame channel, the wall  14   a  being formed of refractory material into a shape for installation on the coupling plane Z—Z. This “flame channel with a flame buffer plate” is then fastened by mounting flanges formed on the above-mentioned coupling plane Z—Z. 
     FIG. 2 is an exploded perspective view showing the “flame channel with a flame buffer plate” of the air-cooled ammonia absorption refrigerator in the present embodiment shown in FIG. 1 above, being detached along the plane Z—Z. 
     The flame-channel external wall  14   a  in this FIG. 2 illustrates in a detached state the external wall  14   a  shown in FIG. 1 above. The reference numerals  14   b  designate the mounting flanges. 
     In an overview, the flame buffer plate  13  has an inverted T shape, with its lower half of a general rectangle under a tongue projecting upward. 
     In a little closer look, the plate  13  has a broad cross shape, whereas it is more like an inverted cross as compared to the general concept. Of its vertical bar, the portion extending upward is relatively long, and the leg extending downward is extremely short and broad. 
     The intersection of the vertical and horizontal bars (the central portion of the cross) is opposed straight to the flame jet nozzle of the kerosene burner  8  described above, constituting the main body of the flame buffer plate  13 . 
     The upward-projecting tongue  13   b  is wide at the bottom (i.e., the lower half) and gets narrower into a taper as approaching the extremity thereof. There is a definite clearance between the extremity (upper end) of the tongue  13   b  and the ceiling of the flame-channel external wall  14   a . The vicinity thereof constitutes the main path for the curved flame. 
     Comparison between this FIG.  2  and the forecited FIG. 1 shows that major part of the curved flame  9  passes above the tongue  13   b  while some other part of the same runs through the sides of the tongue  13   b.    
     The spaces on both sides of the tongue  13   b  are obliquely above a portion  13   a  that is opposed straight to the above-mentioned burner. Since the tongue  13   b  is wide at its lower half and narrow at its upper half, the gaps by the tongue are narrow at the lower and wide at the upper. The flame passing therethrough is influenced in distribution by the points as follows: 
     For convenience of description, the following consideration will be made on qualitative comparison between the vicinity of the U portion (a lateral upper side by the tongue) and the vicinity of the D portion shown in FIG.  2 . 
     The U portion is greater in breadth than the D portion, functioning to increase the flame that runs through the U portion. 
     The U-portion pass is a longer way than the D-portion pass. This functions to decrease the flame that runs through the U portion. 
     To take account of the inertia of the flame that collides against the main body  13   a  of the flame buffer plate  13  to turn, the U portion requires relatively smaller turning-radii for the turn, thereby decreasing the amount of the flame passing therethrough. Meanwhile, the D portion only needs relatively greater turning-radii for the turn, increasing the amount of the flame passing therethrough. 
     Calculating to design the quantitative distribution of the flame passing the vicinities of the tongue  13   b  in consideration of the influences described above is not very easy. It is, however, possible for those skilled in the art to obtain the distribution through experiments without any particular difficulties. 
     Here, the discussion has been made on the quantitative distribution of the flame at each detours because the high-temperature combustion gas flows to be fed to the heat transfer fins of the generator  1  should be made uniform in temperature distribution. 
     Accordingly, theoretical elucidation and designing calculation on the quantitative distribution of the flame are not always necessary. Experimental approaches by repeating measurement on the temperature distribution of the combustion gas with various shapes of flame buffer plates are practical in determining the appropriate shall for the flame buffer plate to offer desired temperature distribution. 
     As stated previously, the leg (the portion projecting downward from the horizontal beam) of the cross-like flame buffer plate  13  is extremely broad and short as shown in FIG.  2 . 
     Both the right and left ends of the horizontal broad beam and the lower end of the broad, short leg are fixed to the external wall  14   a . In assembling a combustion system by the method of the present invention, it is desirable to install the “flame-channel external wall  14   a  with a flame buffer plate  13 ” as illustrated in the figure. 
     Since the leg of the flame buffer plate  13  is broad and short as mentioned above, flame bypasses  13   c  formed on lower right and left of the main body  13   a  opposed straight to the burner are very small in area. Such flame bypasses are provided with an aim to “uniformize the temperature distribution of the combustion gas flows to be fed to the heat transfer fins  1   a .” Experimental approaches are therefore preferable in determining the position, size, and shape of the flame bypasses  13   c.    
     In this FIG. 2, the flame bypasses  13   c  are formed by cutting away part of the flame buffer plate  13 . In embodying the present invention, however, these flame bypasses may be formed by making through-holes or openings in the flame buffer plate. 
     The experiments by the present inventors show that the flame bypasses  13   c  appropriately have a total flow area not greater than 10% the total cross-sectional area of the paths. Flow areas above 10% haze the opposite effect of making nonuniform the temperature distribution of the combustion gas in the periphery of the heat transfer fins, facilitating to cause unfavorable results. Particularly, an increase of the flames running through the bypasses lengthens the bypass flames so that the extremities of the bypass flames approach the heat transfer fins. Therefore, the bypasses must not have very large areas. 
     FIG. 3 is an external perspective view of an embodiment of the air-cooled ammonia absorption refrigerator according to the present invention, the view exclusively illustrating a generator, a curved flame channel, and a heat-shield cover for covering the curved flame channel. Note that the illustration is given in a schematic fashion and therefore it does not exactly present the substantial projections of the members. 
     The reference numeral  14   a  designates an external wall of the curved flame channel, to which the same reference numeral is attached in the forecited FIG.  1 . Opposed to the external wall  14   a  via gaps is the heat-shield cover  15 . This heat-shield cover is formed of metal plates. The present embodiment uses uncoated stainless steel plates therefor. 
     As seen from FIG. 1, the curved flame channel  14  is arranged inside the casing of the air-cooled ammonia absorption refrigerator. Heat radiated from the flame channel  14  therefore increases the temperature inside the casing. Since the casing contains electronic components (not shown) for the control system, an excessive rise in the inside temperature of the casing might cause thermal damage to the electronic components. Thus, the temperature rise inside the casing needs to be suppressed, if possible. 
     In the present embodiment, the external wall  14   a  of the flame channel may be heated up to 300-800° C. Accordingly, the temperature rise inside the casing due to the radiant heat from the external wall  14   a  is not negligible. 
     The radiant heat mentioned above is blocked by the heat-shield cover  15 . In particular, the heat-shield cover  15  favorably has specular gloss on its internal surfaces so that the radiation is reflected to suppress a rise in the temperature of the cover  15  itself. 
     Besides, the heat-shield cover  15  has a cooling-air inlet  15   b  in the vicinity of its lower end. Moreover, a chimney  15   d  is projected upward from the vicinity of the top of the heat-shield cover  15 . 
     In FIG. 1, the heat-shield cover  15  is omitted of illustration. The chimney  15   d  mentioned above, in fact, is projected upward through the casing of the air-cooled ammonia absorption refrigerator to allow communication with the space above the refrigerator. 
     The air inside the refrigerator casing is inhaled through the cooling-air inlet  15   b  (FIG.  3 ). Here, the inhaled air comes into contact with the flame-channel external wall  14   a  to receive heat therefrom for cooling. The air having received the heat to increase in temperature expands to be lighter. This produces free convection so that the air rises up to be released through the chimney  15   d . After this manner, the head-shield cover  15  blocks the radiant heat from the external wall  14   a  of the flame channel and cools the external wall  14   a  by means of convection as well, thereby suppressing the temperature rise inside the casing. 
     As can clearly be seen from the configuration and functions described above, the cooling of the flame-channel external wall  14   a  by the heat-shield cover  15  in the present embodiment requires no cooling fan motor to be installed. This avoids considerable increases in the equipment and material cost for the modification. The absence of cooling fan motors eliminates power consumption in cooling the external wall of the flame channel. The absence of cooling fan motors also eliminates the possibility of flame-channel cooling means producing vibrations and noises. This enables quiet, smooth, and sure cooling of the flame-channel external wall. 
     Now, description will be made as to the reason why in the present invention the cooling of the flame channel is regarded as of importance as described above. That is, when a curved flame channel is provided through the application of the present invention, the curve of the flame channel causes a rise in surface area. This develops a tendency to increase heat radiation from the flame channel. In order to correct the defect, much importance is attached to the suppression of the heat radiation from the flame channel. 
     In applying modifications in a broad sense (including design improvements) to a conventional, gas-fired type air-cooled ammonia absorption refrigerator to constitute the oil-fired type air-cooled ammonia absorption refrigerator shown in FIG. 1 (the embodiment), the kerosene burner  8  is somewhat large as compared to the conventional gas burner. Besides, the new flame channel is greater in outer dimensions due to its curve. Thus, the burner cover previously attached to the casing of the conventional example is removed and replaced with a kerosene burner cover  11   d  fabricated to constitute a modified casing  11 . Among the component members of this modified casing  11 , those on the left of the plane Z—Z in the figure are the same as those of the conventional casing. Thus, the application of this invention method requires only a small amount of cost for the casing work. 
     As described above the modified casing  11  (FIG. 1) is assembled by installing the kerosene burner cover  11   d . By this means, the air-cooled ammonia absorption refrigerator modified into oil-fire type is provided with a style in appearance as a plant appliance, presenting a regular design for marketability. 
     While the present invention is intended to be applied to an air-cooled ammonia absorption refrigerator, a few components can be added to convert the apparatus dedicated for cooling into an apparatus for both cooling and heating. 
     Accordingly, the present invention is also applicable to an air-cooled ammonia absorption cooler heater as long as the cooler heater contains the components that can function as an air-cooled ammonia absorption refrigerator. In other words, even when the apparatus also comprises heating means, the method of applying the present invention to an air-cooled ammonia absorption refrigerator portion of the apparatus to make a gas-fired-to-oil-fired modification thereto and the air-cooled ammonia absorption refrigerator modified into an oil-fired type are considered as fall within the technical scope of the present invention. 
     While there has been described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.