AU8398082A - Evaporator arrangement to be used in a refrigerant circuit - Google Patents

Description

Evaporator arrangement to be used in a refrigerant circuit.

The present invention relates to an evaporator arrangement to be used in a refrigerant circuit, comprising a condenser and a com- pressor, wherein the suction side of the compressor is connected to the evaporator arrangement, and wherein the evaporator arrangement is fed with refrigerant from the condenser through an expansion val¬ ve controlled by means of a sensor.

In connection with evaporator arrangements of the kind re¬ ferred to above It is known to position the temperature sensor upon a suction conduit which connects the evaporator arrangement to the suction side of the compressor. In order that the sensor may control the expansion valve in a stable way It Is necessary that the refrige¬ rant vapours which pass the location at which the sensor Is arranged have such a temperature that the sensor achieves a temperature which is approximately 3-7°C and preferably 5 C higher than the evapora¬ ting temperature which corresponds to the evaporating pressure cau¬ sed by the compressor In the evaporator arrangement. This again necessitates a certain superheating of the refrigerator vapours in the evaporator arrangement. Such superheating on the other hand results in that the capacity of the evaporator arrangement is not fully uti¬ lized. This is due to the fact that the best heat transfer is achieved In an evaporator arrangement, if the filling of the evaporator arran¬ gement with liquid refrigerant is at a maximum. However, when the vapours are to be superheated in order to achieve the temperature difference explained above, such superheating results in that solely refrigerant vapours are present in the last part of the evaporator arrangement, seeing that otherwise such superheating cannot be achieved. However, due to the fact that the heat transfer to vapours is inferior than the heat transfer to liquid, the result, as mentioned above, will be that the evaporator arrangement is not utilized to Its maximum.

The evaporator arrangement according to the present in¬ vention is characterized in that the sensor is arranged upon a part of the evaporator arrangement, which part is coupled in parallel with the remaining part of the evaporator arrangement between the expansion valve and the suction side of the compressor. Moreover, said part of the evaporator arrangement is dimensioned and/or arran¬ ged in such a way with respect to the remaining part of the evapo¬ rator arrangement that the ratio between the portion of the refrige- rant which is fed to the part coupled in parallel, and the heat sup¬ plied to this part is less than the ratio between the portion of the refrigerant which is fed to the remaining part of the evaporator ar¬ rangement and the heat supplied to this remaining part. By means of this arrangement it is achieved that the portion of the refrigerant which is fed to the part coupled in parallel receives more heat per kilogram refrigerant fed thereto than the portion of the refrigerant which Is fed to the remaining part of the evaporator arrangement or, in other words, the heat content of the refrigerant which leaves the part coupled in parallel will be higher than the heat content of the portion of the refrigerant which leaves the remaining part of the eva¬ porator arrangement. This proportioning results in that the neces¬ sary superheating of the refrigerant vapours may be caused in the last part of the part coupled in parallel In such a way that the sen- sor achieves the increased temperature necessary with respect to the evaporating temperature, but due to the fact that this is only the case as regards the part coupled in parallel, the remaining part of the evaporator arrangement may be fully utilized, viz. to the max¬ imum of its capacity. Accordingly, it is achieved that a small part only of the complete evaporator arrangement cannot be used to the full capacity.

An advantageous embodiment of the evaporator arrange¬ ment Is according to the invention characterized In that the first mentioned ratio is so much less than the last mentioned ratio that a superheating of the refrigerant vapours at the outlet end of the part coupled in parallel amounting to approximately 3-7 C and pre¬ ferably 5 C is achieved, whereas substantially no superheating is caused at the outlet end of the remaining part of the evaporator arrangement. By means of this embodiment it is achieved that the evaporator arrangement is used to its maximum capacity, because said temperature difference is the difference which in a secure way will result in a stable control of the expansion valve.

In case the evaporator arrangement comprises more tubes or hoses coupled in parallel and having mutually generally same length, same thickness and same diameter, which e.g. often is the case for evaporator arrangements for heat pumps for heating houses, the sensor preferably, according to the Invention, is arranged at the outlet end of one of the tubes or hoses, and moreover a flow resis¬ tance is provided at the inlet end of said tube or hose. Such arrange- ment is advantageous in that it may be used without considerably changing the production program followed in the manufacturing of evaporator arrangements comprising several tubes or hoses coupled in parallel . The embodiment referred to above is advantageous in the case where the heating conditions as regards the tubes or hoses coup¬ led in parallel are identical . However, there may also be occasions wherein different parts of an evaporator arrangement are supplied with different amounts of heat. This e.g. is the case if the evapora- tor arrangement is subdivided into two or more parts coupled in parallel through which the heating medium in question flows in series . In order also in the latter case to be able to use mutually identical evaporator arrangement parts, the sensor may according to a further embodiment of the invention be arranged at the outlet end of the • part of the evaporator arrangement through which the heating medi¬ um flows first.

The invention will hereinafter be further explained with reference to the drawing, in which

Fig. 1 illustrates a first embodiment of the evaporator arrangement according to the invention, and

Fig . 2 illustrates another embodiment of the evaporator arrangement according to the invention.

In the drawing, 1 designates a refrigerant circuit which as seen in the direction of circulation of the refrigerant comprises: a compressor 2, a condenser 3, a sight glass 4, a filter 5, one side 6 of a heat equalizer which In its entirety is provided with the refe¬ rence numeral 7, a thermostatic expansion valve , 8, a distributing head 9, an evaporator which in its entirety is provided with the reference numeral 10 and the other side 11 of the heat equalizer 7 via which the outlet end of the evaporator 10 is connected to the suc¬ tion side of the compressor 2.

The evaporator 10 Is divided into three parts 14, 15 and 16 coupled in parallel , and in the case illustrated in Fig. 1 , the heating medium for the evaporator is air or water which is circulated through a housing 17 wherein the greater part of the parts 14, 15 and 16 is arranged.

One end of the three parts 14, 15 and 16 of the evaporator is connected to the distributing head 9, and at the other end of the part 14 the sensor 18 for the thermostatic valve 8 is arranged, whereas the other ends of the two other ^"parts 15 and 16 are coupled to each other at a connecting point 19 which is connected with the suction conduit 20 of the compressor 2 at a location positioned after the location at which the suction line 20 Is connected with the other end of the evaporator part 14.

Accordingly, with respect to the remaining parts 15, 16 of the evaporator, the evaporator part 14 constitutes a part which is coupled in parallel, and as mentioned the sensor 18 is arranged at the outlet end of the evaporator part 14. According to the embodiment illustrated in Fig. 1 the parts 14, 15 and 16 are identical per se, i.e. that they have the same length, diameter and wall thickness, but as regards the part 14 a modification of dimension has been made consisting therein that a flow resistance 22 is arranged between the part 14 and the distributing head 9. Accordingly, the three parts 14, 15 and 16 will be fed differently with refrigerant from the distri¬ buting head 9, because the resistance 22 results in that less refrige¬ rant will be fed to the part 14 than to the parts 15 and 16, respec¬ tively. Due to the fact that generally the same amount of heat will be supplied to the parts 14, 15 and 16, according to the arrangement illustrated, from the air or water circulated through the housing 17, the ratio between the portion of the refrigerant fed to the part 14 and the heat supplied to this part will be comparatively small, whereas the ratio between the amount of refrigerant fed to the parts 15, 16 and the heat received by this part will be comparatively high. Accor¬ dingly, per unit of weight of refrigerant, a more intensive heating will result in the part 14 than in the parts 15 and 16, or in other words, the refrigerant portion which leaves the evaporator part 14 will have a higher heat content than the refrigerant portions which leave the evaporator parts 15 and 16, respectively. The resistance 22 is so selected that the amount of refrigerant fed to the evaporator part 14 will be completely evaporated and superheated, approximately 3-7°C, and preferably 5°C, whereas the amounts of refrigerant fed to the evaporator parts 15 and 16 are just evaporated. Accordingly, the capacity of the parts 15 and 16 will be utilized to its maximum due to the fact that heat transfer in the parts 15 and 16 will take place to liquid refrigerant along the full length of the parts 15 and 16, and it is only the very last end of the evaporator part 14 which will not be utilized to its maximum, because vapours will be con- tained therein to which the heat transfer is less than when heat is transferred to liquid refrigerant.

The high degree of utilization of the evaporator explained above is of particular importance In cases where the temperature 5 difference between the heating medium and the evaporating tempera-^{4 f}- ture is rather small. This is e.g. the case, where heat pumps are concerned, wherein the condenser 3 serves as heating source, and wherein the heating medium for the evaporator is constituted, e.g . by water from a well, seawater, heat from surrounding soil or other 10 heating sources of comparatively low temperatures, because the tem¬ perature difference between the temperature of the heating medium and the evaporating temperature of the refrigerant is utilized to its maximum. This is due to the fact that the temperature of the greater part of the evaporator is maintained at the evaporating temperature 15 of the refrigerant at the pressure concerned.

According to the embodiment illustrated in Fig. 1 , an eva¬ porator is used consisting of three parts 14, 15 and 16 which, except for the resistance 22 inserted into the evaporator part 14, are iden¬ tical. Such embodiment is advantageous, because identical structural 20 elements may be used for all the evaporator parts, but it will be understood that nothing prevents the construction of an evaporator arrangement according to the present invention consisting of mutu¬ ally different parts. However, due care must be taken that the con¬ dition referred to above is fulfilled, viz. that the part 14, which is 25 coupled in parallel and upon which the sensor 18 is- arranged, is so dimensioned with respect to the remaining parts 15 and 16 of the evaporator arrangement that the ratio between the portion of the refrigerant which is fed to the part 14 coupled in parallel and the heat which is supplied to this part 14 is less than the ratio between _t 30 the portion of the refrigerant which is fed to the remaining part 15 and 16 of the evaporator arrangement and the heat which this remai- { nϊng part of the evaporator arrangement receives. By such dimension- ϊng it is possible to obtain the superheating referred to above solely in the part 14 which is coupled in parallel.

35 Instead of achieving the ratio explained above by feeding less refrigerant to the part of the evaporator arrangement upon which the sensor is arranged, a relatively increased heating of the part of the evaporator element coupled in parallel and upon which the sensor is arranged may be used . Such embodiment is illustrated in Fig . 2, wherein the same references have been used for the same parts as in Fig. 1.

From Fig. 2 it will be seen that the evaporator 10 shown therein is divided Into two evaporator parts 30 and 31 which are coupled in parallel and through which a heating medium, e.g. air or water, flows in series as indicated by means of arrows 32. Accor¬ ding to the embodiment illustrated in Fig. 2 the two evaporator parts 30 and 31 are identical, and equal amounts of refrigerant are fed to the two parts. However, due to the fact that the evaporator part 31 is the first through which the heating medium flows, and due to the fact that the evaporating temperature in the two evaporator parts is the same, the evaporator part 31, through which the heating medium flows first, will receive a greater amount of heat than the evaporator part 30, through which the heating medium flows last, simply because the temperature difference between the heating medium and the refri¬ gerant is greater in the first evaporator part. The sensor 18 of the expansion valve 8 is arranged after the evaporator part 31 , and the feeding of the refrigerant to the evaporator part 31 Is adjusted In such a way with respect to the heating medium flowing therethrough that refrigerant vapours which leave the evaporator part 31 achieve such a superheating that a temperature is applied to the sensor 18 which is approximately 3-7°C and preferably 5°C higher than the evaporating temperature. Accordingly, also in this instance a stable control is achieved and a high utilization degree of the evaporator is achieved, due to the fact that the refrigerant in the evaporator

_* part 30 needs no heating beyond the temperature corresponding to the temperature of saturated refrigerant vapour at the evaporating pressure concerned. According to the embodiment shown In Fig. 2, two identical evaporator parts 30 and 31 are used, but it will be understood that this need not be the case if only the condition ex¬ plained above is fulfilled, viz. that the evaporator part 31 is arran¬ ged in such a way with respect to the remaining part 30 of the eva¬ porator arrangement that the ratio between the portion of the refrige¬ rant which is fed to the part 31 coupled in parallel and the heat sup- plied to this part is less than the ratio between the portion of the refrigerant which is fed to the remaining part 30 of the evaporator arrangement and the heat which is supplied to the remaining part of the evaporator arrangement.

Claims (4)

P a t e n t C l a i m s :

1. Evaporator arrangement to be used in a refrigerant circuit, comprising a condenser (3) and a compressor (2), wherein

*- r the suction side of the compressor is connected to the evaporator

5 arrangement (10), and wherein the evaporator arrangement (10) is fed with refrigerant from the condenser (3) through an expansion valve (8) controlled by means of a sensor (18), c h a r a c t e ¬ r i z e d in that the sensor (18) is arranged upon a part (14,31) of the evaporator arrangement (10) which part (14;31) is coupled in 10 parallel with the remaining part (15,16;30) of the evaporator arrange¬ ment (10) between the expansion valve (8) and the suction side of the compressor (2) and is dimensioned and/or arranged in such a way with respect to the remaining part (15,16;30) of the evaporator arrangement (10) that the ratio between the portion of the refrigerant 15 which is fed to the part (14;31) coupled in parallel and the heat sup¬ plied to this part (14; 31) is less than the ratio between the portion of the refrigerant which is fed to the remaining part (15,16,30) of the evaporator arrangement (10) and the heat supplied to this re¬ maining part (15,16;30) of the evaporator arrangement (10). 20

2. Evaporator arrangement according to claim 1, c h a r a c t e r i z e d in that the first mentioned ratio is so much less than the last mentioned ratio that a superheating of the refrigerant vapours at the outlet end of the part (14;31) coupled in parallel amounting to approximately 3-7 C and preferably 5 C is achie- 25 ved, whereas substantially no superheating is caused at the outlet end of the remaining part (15,16,30).

3. Evaporator arrangement according to claim 1, wherein the evaporator arrangement (10) comprises more tubes (14,15,16) or hoses coupled in parallel and having mutually generally same

30 length, same thickness and same diameter, c h a r a c t e r i z e d in that the sensor (18) is arranged at the outlet end of one of the tubes (14) or hoses, and that a flow resistance (22) is provided at the inlet end of said tube (14) or hose.

4. Evaporator arrangement according to claim 1, wherein 35 the evaporator arrangement comprises two or more parts (30 and 31) coupled in parallel, through which the heating medium in question flows in series, c h a r a c t e r i z e d in that the parts (30,31) coupled in parallel are mutually identical and that the sensor (18) is arranged at the outlet end of the part (31), through which the hea¬ ^v