Patent Publication Number: US-3874193-A

Title: Absorption refrigerator with additional means for defrosting the refrigerator

Description:
United States Patent 11 1 1111 3,874,193 Reistad 5] Apr. 1, 1975 ABSORPTION REFRIGERATOR WITH [56] References Cited ADDITIONAL MEANS FOR DEFROSTING N] STATES PATENTS THE REFRIGERATOR 2,240,175 4/1941 Coons et al 62/110 x 75 Inventor; Bengt Reistad R i Bromma, 2,468,104 4/1949 Phillips 62/110 X Sweden 3,177,675 4/1965 Kogel 62/490 x 3,807,189 4/1974 Eber et a1, 62/490 X [73] Assignee: Aktiebolaget Electrolux, Stockholm, 1  
  Sweden Primary Exa11zinerWilIiam F. ODea 22 i Man 4 1974 Assistant ExaminerPeter D. Ferguson [21] Appl. No.: 447,484 ABSTRACT I An absorption refrigeration apparatus operating with [30] Forelg Apphcanon Prmmy Data inert gas and having means for lifting liquid from one Mill. 2, I973 Sweden 73029548 level to a level means can be used to achieve a well controlled defrosting of the refrigera- [52] U.S. CI. 62/490 i apparatus under all normal operating conditions [51] Int. Cl. thereof [58] Field of Search 61/110, 490, 491  
 6 Claims, 3 Drawing Figures 21 &#39;1 l I1 11 10 II II 34 77 n 20 II II 12 1- ll 76 13 {l 14 BACKGROUND OF THE INVENTION An absorption refrigeration apparatus is known which operates with inert gas and has means using collected liquid for control of apparatus functions. In prior art, liquid has been supplied to such means either by a heat operated pump or from a conduit in which condensate is present and which is leading such condensate to the means. It is also known in the gas circulation system of an absorption refrigeration apparatus to have a liquid seal being normally open to permit circulation of gas and being temporarily closed to block the gas circulation. After the blocking period, the seal is emptied by a siphon. During the blocking period, generation of cold in the evaporator system of the apparatus ceases and thus defrosting of the evaporator part occurs. After the liquid seal has been emptied, liquid is again collected in it either by leading condensate of the working media present in the gas circulation system into the liquid seal or by leading vapor of the working media from the boiler system of the refrigeration apparatus towards the liquid seal, which vapor is caused to condense to a certain extent in the supply conduit. Both these methods for solving the problem of bringing about defrosting of the refrigeration apparatus involve certain disadvantages. For example, if condensate from the gas circulation system is used, defrosting will be very much dependent on the operational conditions of the apparatus because the condensation of working media in the conduits concerned varies to a great extent with different ambient temperatures or with the loads on the refrigerator operated by the apparatus. If instead of the foregoing method the other method of condensation of hot vapors from the vapor space in the boiler system of the apparatus is used, this will entail the disadvantage that part of the heat is removed from the boiler system, among other disadvantages. Also regulation of the quantities of condensate collected may involve difficulties. In addition to these disadvantages, it is difficult to construct the apparatus such that a modification intended for automatic defrosting can be readily obtained from a manufacturing point of view by adding an extra part to an embodiment intended to operate without defrosting.  
  It is an object of the present invention to provide means in the refrigeration apparatus for lifting liquid from one level to a higher level without heat supply to the lifting means.  
  It is another object of the present invention to provide a simple additional part to the refrigeration apparatus which is connected into the system to thereby achieve a well controlled defrosting under all normal operating conditions.  
  The invention will now be more fully described with reference to the accompanying drawings, in which:  
  FIG. 1 is a diagrammatic view of the absorption refrigeration apparatus having the additional automatic defrosting installation, and with the heat insulation removed from the boiler;  
  FIG. 2 is a view of certain details of construction of the automatic defrosting installation of FIG. 1 on an enlarged scale; and  
  FIG. 3 is a modified embodiment of the automatic defrosting installation shown in FIGS. 1 and 2.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the refrigeration apparatus shown is the known type utilizing water, ammonia, and hydrogen in the cycle. In this cycle, the water, ammonia, and hydrogen act as an absorption solution, a refrigerant, and a pressure equalizing inert gas, respectively. However,other media may be used.  
  The refrigeration apparatus during the normal generation of cold can be controlled by a thermostat (not shown), which connects and disconnects the electrical circuit depending upon the required cooling need. Electric power is supplied through the wires 10 to the electric heating cartridge 11 positioned in a metal sleeve 12 which is in heat conductive relationship with the boiler 14 along the line 13. The outer conduit 15 of the heat exchanger contains absorption solution weak in refrigerant and supplied from the outer pipe of the boiler. This solution is conveyed through a conduit 16 and eventually to the upper part of the absorber 17 of the apparatus. In the absorber, the solution flows downwardly while absorbing refrigerant vapor from the rising rich mixture of refrigerant vapor and inert gas. When the solution has passed through the absorber 17 in which it is enriched in refrigerant, it is collected in an absorber vessel 18 from which it is supplied by a conduit 19 to the liquid circulating pump 20 in the boiler 14. The pump 20 forms an inner conduit in the liquid heat exchanger. As seen in FIG. 1, the pump 20 is located concentrically in the vertical part, the upper end 21 of which is closed.  
  Vapors emanating from the pump 20 and boiler 14 are conveyed in a vapor conduit. 22 to the condenser 24 of the refrigeration apparatus provided with fins 23. The evaporator of the apparatus comprises evaporator parts 26 and 27 and a conduit 25 is heat-conductively connected to both evaporator parts 26 and 27 and the refrigerant condensate formed. in the condenser 24 passes through the conduit 25 to the highest point in the evaporator system at one end of the evaporator part 27. At the same location, weak inert gas is supplied which has been pre-cooled in the inner conduit 28 of the evaporator system and comes from the absorber 17. Thus, the refrigerant and the weak gas are in parallel flow through the evaporator part 27 which forms the low temperature evaporator, and thereafter through the evaporator part 26 which forms the high temperature evaporator, and through a gas heat exchanger 29 to the conduit 30. The latter leads to a vapor space 31 in the absorber vessel 18 from which the gas is led upwardly through the absorber 17.  
  The gas mixture which is weak in refrigerant appears at the upper end of the absorber 17 and is conveyed through a conduit 32 to the top part of a vessel 33 which, in a known manner, serves as a liquid seal in the gas conduit. A siphon 34 extends to the bottom part of the vessel 33 and transfers the liquid content of the vessel 33 to the absorber vessel 18 when the liquid in the vessel 33 has risen above the level 35. The vessel 33 is provided with a conduit 36 which is open in its bottom end, the latter being on a level 37 located slightly below the highest level 35 of the siphon 34. As long as the liquid in the vessel 33 is at a level below the level 37 adjacent to the bottom opening of the conduit 36, the weak gas is conveyed from the conduit 32 downwardly in the vessel 33 and upwardly through the conduit 36 which outside of the vessel 33 has a laterally disposed part 38 that is inclined downwardly to connect with the conduit 39. The latter conduit is an extension of the gas conduit 29 passing through the evaporator system and extends as far downwardly to be submerged in the liquid held in the absorber vessel 18.  
  The vessel 33 is provided with a liquid seal formed by collected liquid. In this regard, FIG. 1 discloses a vent conduit 40 connected at one end to the condenser 24 and directly connected&#39;to the conduit 16 in which weak absorption solution is supplied to the absorber 17. As seen in FIGS. 1 and 2, the vent conduit 40 and the conduit 16 form the same pipe and a connecting conduit 41 is shown between the conduit 16 and the absorber 17. The connecting conduit 41 is connected to the absorber 17 at a level 42. The connecting conduit 43 forms a bubble pump between the conduit 16 and the vessel 33. As seen in FIG. 2, the conduit 43 is connected to the conduit 16 at a level 44 located below the level 42 and to the vessel 33 at a level 45 above the level 42 where the liquid intake to the absorber 17 is situated.  
  It should be noted that the use of hydrogen as an inert gas, and ammonia and water as the other working medium results in that the solubility of hydrogen in the solution is bound by the physical laws, and the solubility is directly proportional to the partial pressure of hydrogen above the free liquid surface. The solubility further depends on temperature; however, in practice, this dependence is insignificant. The transport is accomplished with such an amount of hydrogen and so constantly under different operating conditions that it can be used to operate the bubble pump 43 and transfer the desired quantities of weak absorption solution to the vessel 33. The level 42 at the absorber intake can be adjusted relative to the levels 44 and 45 at the inlet and outlet of the bubble pump 43 as well as adjusting the relation between the levels 35, 37, and 46, the latter being the end of the siphon 34 opening into the vessel 33. These adjustments result in the defrosting of the evaporator of the absorption refrigerator at the desired time and during the same time approximately for each defrosting. By changing the relation between the levels near the bubble pump, the liquid supply to the vessel 33 can be varied and by adjusting the levels in the vessel 33, it is also possible to modify the filling time of the liquid seal. Accordingly, as described above, there are two possible ways of adjusting the desired times for defrosting.  
  When the gas mixture in the absorber leaves the absorber part 32, it contains substantially all hydrogen with some ammonia vapor and a small portion of water vapor. When the gas is cooled in the inner conduit 28 of the gas heat exchanger 29, a small quantity of water vapor and ammonia vapor will condense. The resultant condensate flows downwardly through the conduit 39 and is drained in the absorber vessel 18. The condensate instead of flowing to the absorber vessel 18 may be conducted to another part of the absorber, for example, to the highest point of the absorber. However, the condensate should never be permitted to flow down into the vessel 33. If the condensate found its way into the vessel 33, the time for filling the vessel from the level 46 to the level 37 would be much shorter than otherwise; but the time for filling from the level 37 to the level 35 would remain the same as has been disclosed hereinbefore. In accordance with the teachings of the present invention, the time represented by the difference of the levels 46-37 is about 20 times longer than the time represented by the difference between the levels 37-35; and obviously, it would not be desirable to increase the filling velocity during the interval 46-37.  
  The condenser 24 contains ammonia in vapor and liquidphase and in addition contains an insignificant quantity of water in vapor and liquid phase and a quantity of hydrogen depending upon the ambient temperature. With regard to the latter, there is more hydrogen in the condenser at low ambient temperature than at high ambient temperature. Hydrogen is conveyed to or from the condenser by the vent conduit 40 at variations of the ambient temperature. Furthermore, additional hydrogen will be continually supplied to the boiler 14 with the rich solution from the absorber vessel.  
  As seen in FIGS. 1 and 2, the defrosting time depends largely on the differences in the distance between the levels 35 and 37, i.e., the distance from the top of the siphon 34 to the level 37 at the lower opening of the conduit 36 through which the gas flow is blocked during defrosting. In large scale production, the relative position of the levels 35 and 37 may differ somewhat and this may influence the defrosting time from one apparatus to another.  
  FIG. 3 shows another embodiment of the present invention which has been developed in order to make the apparatus less sensitive to production tolerances. In this alternate construction, the gas blocking unit is provided with a larger horizontal cross-sectional area between the first and the second levels than between the second and third levels. In this construction, weak liquid is supplied through conduit 16 and conduct 41 to the absorber 17. Inert gas flows downwardly through the conduit 40 and will press some liquid up through conduit 43 into the left hand branch 47 of a U-shaped conduit. The upper end of branch 47 is connected to the absorber 17 so that inert gas, weak in refrigerant, passes into the U-shaped conduit, the other branch 48 of which is connected to the evaporator (not shown) through the gas heat exchanger 29. The U-shaped conduit 47, 48 is located in a vessel 49 and opens into the vessel through hole 50 in the bight of the U. As seen in FIG. 3, a siphon 34 is arranged with its inlet opening located just above the bottom of the vessel 49 at the level 46. The rounded top of the siphon is positioned inside the vessel 49 at the level 35. Liquid pumped into the U-shaped conduit 47, 48 through the conduit 43 flows through the hole 50 and is collected in the vessel up to the level 37. When further liquid is supplied to the U- shaped conduit, it cannot rise within the entire vessel 49 because above the liquid level there is an upper enclosed space containing inert gas and vapor. Thus, above the level 37, the liquid will rise only inside the two legs 47, 48 of the U-shaped conduit. When the liquid reaches the level 35, the siphon 34 will be active and lower the liquid to the level 46. The liquid in the apparatus rises slowly from the bottom of the vessel 49 to the level 37. Thereafter, the liquid rises very fast and therefore, it is possible to have a comparatively large distance between the levels 37 and 35.  
  It should be apparent that the present refrigeration apparatus can be easily manufactured in large scale production. Moreover, although the illustrations herein are on one plane for the sake of clarity, it is within the scope of the present invention to position the parts of the refrigeration apparatus in other ways relative to each other, which are more suitable from the point of view of ease of manufacture.  
 What is claimed is:  
  1. In an absorption refrigeration apparatus having an inert gas andprovided with a circuit for absorption liquid working medium, a gas circulation system including an evaporator and absorber, a vapor expulsion unit, a condenser connected to said vapor expulsion unit for delivering liquid to the evaporator to produce a refrigerating effect, the improvement comprising; a vessel in said apparatus, means for transfering the liquid working medium from one part of the refrigeration apparatus to said vessel located at a higher level than said one part, a vent pipe conducting gas from said condenser, a first conduit connecting said vent pipe to said vessel, said first conduit functioning as a bubble pump by means of said inert gas being drawn from said condenser through said vent pipe, and a second conduit connected to said vent pipe and having liquid therein, the level of liquid in said bubble pump when no gas is supplied being located above the connection of said vent pipe to said pump but below the connection of said pump to said vessel.  
  2. In an absorption refrigeration apparatus having an inert gas and provided with a circuit for absorption liquid working medium, a gas circulation system including an evaporator and absorber, a vapor expulsion unit, a condenser connected to said vapor expulsion unit for delivering liquid to the evaporator to produce a refrigerating effect, the improvement comprising; a defrosting arrangement for said refrigeration apparatus having a vessel and wherein said gas circulation system is provided with a liquid seal in said vessel, said seal being temporarily open to permit the circulation of a gas and emptying said liquid seal in said vessel after said blocking period, a vent pipe conducting gas from the condenser, a first conduit connecting said vent pipe to said vessel, said first conduit functioning as a bubble pump by means of said inert gas being drawn from said condenser through said vent pipe, a second conduit connected to said vent pipe and conducting weak absorption liquid to said vent pipe, and a branch pipe connecting said second conduit to said absorber, said bubble pump being connected to said seal at a point higher than the-inlet of said branch pipe to said absorber.  
  3. An absorption refrigeration apparatus as claimed in claim 1 wherein said absorber is provided with one gas-conveying conduit connected to the top of said seal, and another gas-conveying conduit in said seal having a part extending outside said seal, said one gasconveying conduit and said part of the other gasconveying conduit being operatively connected to said liquid seal and inclined relative to said seal whereby liquid working media in said conduits flow in the direction from the liquid seal through said conduits.  
  4. An absorption refrigeration apparatus as claimed in claim 1 wherein said absorber is provided with an extension in the form of a U-shaped pipe having legs which are gas-conveying conduits, said conduits being operatively connected to said liquid seal and being inclined so that the liquid working media flow in the direction from the liquid seal through said conduits.  
  5. An absorption refrigeration apparatus as claimed in claim 1 wherein a gas-blocking means is provided in said vessel with a larger liquid collecting area below the gas flow blocking level than above this level.  
  6. An absorption refrigeration apparatus as claimed in claim 5 further comprising a siphon in said vessel having a top level above the gas flow blocking level so as to lower the liquid in the vessel to a predetermined level below the gas flow blocking level.