Refrigeration apparatus

Abstract: The invention relates to a refrigeration apparatus comprising a condenser means (2), evaporator means (4) and compressor means (6) in which a first reservoir (18) acting as a refrigerant accumulator is positioned in the refrigerant flow path between the condenser means (2) and the evaporator means (4) and, in the example shown, wholly encloses a second reservoir (26) which acts as a receiver and is positioned between the evaporator means (4) and the compressor means (6) so that there is direct heat exchange between the two reservoirs to cool the refrigerant in reservoir (18) before entry into the evaporator means (4), as the refrigerant in reservoir (26) is heated before it enters the compressor means (6).

Description: The invention is concerned with improvements in or relating to a refrigeration apparatus operating in a vapour compression cycle, and a method of operating this refrigeration apparatus. In attempts to improve the reliability and efficiency of a compression refrigeration system a number of factors should be taken into consideration, including the protection of the compressor and a satisfactory level of efficiency of operation of the evaporator. It is known to gain an improved level of evaporator efficiency by subcooling the liquid refrigerant supply to the expansion valves associated with the evaporators and that a low vapour temperature (superheat) attained at the evaporator outlet is beneficial to the performance of the evaporator. However, there is the risk that there may be refrigerant in liquid form present in the vapour which is then carried over to the compressor. To avoid this, a higher vapour temperature at the inlet to the compressor means would be required. This problem may be dealt with by providing an additional source of heat to the vapour flow prior to the compressor inlets. US-A-3 872 687 discloses a refrigeration apparatus comprising condenser means (84), evaporator means (86) and compressor means (82) and adapted to operate a flow path of refrigerant fluid, in which there is provided in a first portion (100, 102) of said flow path between said condenser means (84) and said evaporator means (86) a first reservoir (98) adapted to contain a quantity of refrigerant in liquid from which reservoir (98) said flow path is provided with fluid, there being further provided in a second portion (92) of said flow path between said evaporator (86) and said compressor means (82) a second reservoir (96) adapted to receive and retain an accumulated quantity of refrigerant in vapour form from the evaporator means (86) so as to enable the transfer of the refrigerant vapour while retained in the second reservoir (96) of sufficient heat from the liquid refrigerant in the first reservoir (98) to raise the temperature of the vapour entering inlets to the compressor means (82), said second reservoir (96) being contained in the first reservoir (98), outer walls of the second reservoir (96) being spaced from inner walls of the first reservoir (98), such that, in use, the second reservoir (96) is in heat exchange contact with refrigerant in the first reservoir (98). US-A-3 084 523 discloses a refrigeration apparatus comprising condenser means, evaporator means and compressor means and adapted to operate a flow path of refrigerant fluid, in which there is provided a first portion of said flow path between said condenser means and said evaporator means a first reservoir (12) adapted to contain a quantity of refrigerant in liquid form from which said reservoir said flow path is provided with fluid, there being further provided in a second portion of said flow path between said evaporator means and said compressor means a second reservoir (14) adapted to receive and retain an accumulated quantity of refrigerant in vapour form from the evaporator means so as to enable the transfer to the refrigerant vapour while retained in the second reservoir (14) of sufficient heat from the liquid refrigerant in the first reservoir (12) to raise the temperature of the vapour entering inlets to the compressor means, said second reservoir being contained in the chamber of the first reservoir so as to be in heat exchange contact with fluid therein. According to a first aspect of the present invention there is provided a refrigeration apparatus comprising condenser means, evaporator means and compressor means and adapted to operate a flow path of refrigerant fluid, in which there is provided in a first portion of the flow path between the condenser means and said evaporator means a first reservoir adapted to contain a quantity of refrigerant in liquid form from which reservoir the flow path is provided with fluid, there being further provided in a second portion of the flow path between the evaporator means and the compressor means a second reservoir adapted to receive and retain an accumulated quantity of refrigerant in vapour form from the evaporator means so as to enable the transfer to the refrigerant vapour while retained in the second reservoir of sufficient heat from the liquid refrigerant in the first reservoir to raise the temperature of the vapour entering inlets to the compressor means, wherein the second reservoir is wholly contained in the first reservoir, outer walls of the second reservoir being spaced from inner walls of the first reservoir, such that, in use, the second reservoir is surrounded by and in direct heat exchange contact with refrigerant in the first reservoir and wherein further the second reservoir is situated substantially within a lowermost portion of the first reservoir. Thus, heat at an undesirable level in the high pressure portion of the flow path is transferred to the unduly cool, liquid-entraining low pressure vapour portion of the flow path by an efficient and practical apparatus. In this way, a number of advantages are gained. Firstly, no additional heat source is required for the compressor inlet region. Secondly, the presence of the second reservoir greatly enhances the transfer of heat to the retained refrigerant vapour in the second reservoir since the vapour is maintained in heat-exchange conditions for a much longer period than in conventional heat exchangers in which the relatively high rate of flow through comparatively short lengths of pipes results in generally less efficient heat exchange. Moreover, the inclusion of the second reservoir within the first reservoir enables the entire apparatus to comprise a lay-out which is compact and efficient, requiring little or no maintenance in continuous operation over a number of years. According to a second aspect of the present invention there is provided a method of operating a refrigeration apparatus according to the first aspect comprising provision of direct heat exchange between refrigerant fluid in a first reservoir , being a refrigerant accumulator, and refrigerant vapour in a second reservoir, being a refrigerant receiver, wherein the second reservoir is wholly contained within the first reservoir, outer walls of the second reservoir being spaced from inner walls of the first reservoir, whereby refrigerant in the first reservoir is cooled prior to entry into evaporator means of the apparatus and refrigerant in the second reservoir is thus heated prior to entry into compressor means of the apparatus, and wherein further the second reservoir is situated substantially within a lowermost portion of the first reservoir. There will now be described an example of an apparatus and method according to the invention. It will be understood that the description, which is intended to be read with reference to the drawings, is given by way of example only and not by way of limitation. In the drawings:- Figure 1 is a flow diagram of a refrigeration system operating in apparatus according to the invention; Figure 2 is a top view of two reservoirs of the apparatus; Figure 3 is a side elevational view showing internal details of the reservoirs of Figure 2 in broken lines; Figure 4 is a cross section on lines IV-IV of Figure 2; and Figure 5 is a view of apparatus according to the invention received within a compact housing assembly. Referring to Figure 1, the system comprises condenser means 2, evaporator means 4, and compressor means 6, arranged to provide a flow path for a refrigerant fluid such as Freon (R.T.M.) or a suitable CFC-free formulation. The condenser means 2 comprises two coil sections 8, 10 and four associated fans 12. The condenser means 2 receives heated refrigerant in high pressure vapour form through line 14 from the compressor means 6 and high pressure liquid refrigerant then passes to the evaporator means 4 through a line 16 from each coil, each line comprising a portion 16 a , leading via a reservoir 18 to a portion 16 b , as will be explained below. Line 16 b leads to expansion valves 19 of the evaporator means 4 which comprises three evaporator coils 20 representative of the numerous coils that may be associated with various refrigerated units in an integrated system of fixtures. The expansion valves 19 each meter quantities of liquid refrigerant to each coil in a conventional manner. Outlet lines 22 from each coil connect with a main suction line 24 to carry refrigerant in vapour form via a second reservoir 26 to a series of lines 28, each leading to one of four compressors 30 of the compressor means 6. The low pressure vapour is thus converted to high pressure vapour and passes from outlet lines 32 to a header line 34, via an oil separator 36, to line 14 and enters the condenser means 2 described above. As already mentioned above, the operation of the evaporator means 4 is optimised when the liquid refrigerant is supplied to the expansion valves 19 at as cool a temperature as practical. At the same time, it is beneficial to the operation of the compressor means 6, if the vapour entering from the evaporators does not entrain refrigerant in liquid form. This risk is reduced if the vapour is superheated. It is therefore convenient to arrange for heat exchange to take place between the refrigerant in line 16 (16 a , b ) and that in lines 24, 28. This heat exchange is achieved in the present example by the provision of the two reservoirs, 18 and 26. These two reservoirs are illustrated in more detail in Figures 2 to 4. The first reservoir 18 is provided with inlets for the lines 16 a from the condenser means 2 and holds a retained quantity of refrigerant at an operating temperature approaching the condensing temperature. Surrounded by the retained quantity of refrigerant is the second reservoir 26, which by being situated at a level towards the base of the first reservoir 18, reduces the amount of refrigerant required in the reservoir 18 to provide a liquid seal to the outlets. The main suction line 24 is connected to the reservoir 26 so as to supply cold refrigerant vapour from the evaporator means 4 at a temperature of approaching the evaporating temperature. The temperature of the refrigerant in the reservoir 18 is cooled to a more beneficial working temperature. Because of the advantage gained by the use of the invention, in a typical installation as in the present example, the temperature gain between the inlet and the outlet of the reservoir 26 will be found to be approximately 5°K (e.g. 15°C to 20°C), and the temperature reduction between the inlet and the outlet of the reservoir 18 about 4°K (e.g. 35°C to 31°C). From this it is possible to assess the coefficient of performance of the compressors to have been improved by upto 10% compared with conventional arrangements. A further advantage of the arrangement described above is that it is readily incorporated into a compact and economical unit as is shown in Figure 5. The reservoirs 18, 26 are mounted low in the arrangement between the compressor means, the outlets 28 of suction line 24 being connected to the compressors directly. Conveniently, the four compressors 30 are arranged as two on each side of the reservoirs 18, 26, which allows for a simple distribution of suction line pipes and conduits. Reservoir 26 allows a correct oil return to operational compressors. A control panel 38 is provided above the arrangement and the four fans 12 are set in a housing 40 which encloses the unit. Advantageously, the compressor chamber is acoustically lined to damp noise, and provided with adequate ventilation.

Claims: A refrigeration apparatus comprising condenser means (2), evaporator means (4) and compressor means (6) and adapted to operate a flow path (16,24) of refrigerant fluid, in which there is provided in a first portion (16) of the flow path between the condenser means (2) and said evaporator means (4) a first reservoir (18) adapted to contain a quantity of refrigerant in liquid form from which reservoir (18) the flow path is provided with fluid, there being further provided in a second portion (24) of the flow path between the evaporator means (4) and the compressor means (6) a second reservoir (26) adapted to receive and retain an accumulated quantity of refrigerant in vapour form from the evaporator means (4) so as to enable the transfer to the refrigerant vapour while retained in the second reservoir (26) of sufficient heat from the liquid refrigerant in the first reservoir (18) to raise the temperature of the vapour entering inlets to the compressor means (6), wherein the second reservoir (26) is wholly contained in the first reservoir (18), outer walls of the second reservoir (26) being spaced from inner walls of the first reservoir (18), such that, in use, the second reservoir (26) is surrounded by and in direct heat exchange contact with refrigerant in the first reservoir (18) and wherein further the second reservoir (26) is situated substantially within a lowermost portion of the first reservoir (18). An apparatus as claimed in claim 1, wherein the first reservoir (18) comprises a chamber. An apparatus as claimed in claim 1 or claim 2, wherein the first reservoir (18) provides an inlet (16a) in an uppermost portion thereof. An apparatus as claimed in any preceding claim, wherein the first reservoir (18) provides an outlet (16b) in an uppermost portion thereof which communicates with the lowermost portion of the first reservoir (18) via a tube located in the first reservoir (18). An apparatus as claimed in any preceding claim, wherein the second reservoir (26) provides an inlet (24) and at least one outlet (28) in an uppermost portion thereof. An apparatus as claimed in claim 5, wherein the inlet (24) and at least one outlet (28) of the second reservoir (26) communicate with respective lines which pass through an uppermost portion of the first reservoir (18). An apparatus as claimed in any preceding claim, wherein the condenser means (2), evaporator means (4) and compressor means (6) are contained within a housing, the reservoirs (18,26) being arranged at a low level within the housing below that of the condenser means (2) and fans (12) associated therewith. A method of operating the refrigeration apparatus as claimed in any of claims 1 to 7 comprising provision of direct heat exchange between refrigerant fluid in the first reservoir (18), being a refrigerant accumulator, and refrigerant vapour in the second reservoir (26), being a refrigerant receiver, wherein the second reservoir (26) is wholly contained within the first reservoir (18), outer walls of the second reservoir (26) being spaced from inner walls of the first reservoir (18), whereby refrigerant in the first reservoir (18) is cooled prior to entry into evaporator means (4) of the apparatus, and refrigerant in the second reservoir (26) is thus heated prior to entry into compressor means (6) of the apparatus, and wherein further the second reservoir (26) is situated substantially within a lowermost portion of the first reservoir (18).

Inventors: OGILVIE GRAEME, OGILVIE, GRAEME
Applicants: HUSSMANN EUROP LTD, HUSSMANN (EUROPE) LIMITED
Application year: 1995
Main classification: F25B40
IPC codes: F25B5, F25B40