WO2007074094A1

WO2007074094A1 - A cooling device

Info

Publication number: WO2007074094A1
Application number: PCT/EP2006/069810
Authority: WO
Inventors: Serdar Kocaturk; Sabahattin Hocaoglu; Yalcin Guldali; Burak Asureciler
Original assignee: Arcelik Anonim Sirketi
Priority date: 2005-12-29
Filing date: 2006-12-18
Publication date: 2007-07-05
Also published as: CN101351677B; CN101351677A; EP1966549A1; KR101011214B1; EP1966549B1; KR20080081909A

Abstract

By way of the present invention, the heating effect of the refrigerant migration that takes place in an on /off operating cooling system is reduced, and the refilling of the evaporator (5) with the refrigerant at the start of the next compressor (2) on period is improved.

Description

Description A COOLING DEVICE

[0001] The present invention relates to a cooling device wherein the refrigerant migration is directed.

[0002] If no precautions are taken during the off cycle of the compressor in particularly the cooling devices (refrigerator, deep freezer, air conditioner etc.) having a cyclical cooling system, refrigerant passage occurs from the condenser to the evaporator until the suction line and the discharge line pressures are balanced. This condition, called refrigerant migration, results in the overheating of the ambient temperature regionally in the cabin inner portions corresponding to the first evaporator passages wherein particularly the evaporator inlet is situated. The temperature in this region and hence the thermal load of the cooling cabin increases due to the refrigerant migration effect. This condition brings an additional thermal load inside the cooling cabin and also prevents a homogeneous distribution of temperature in the cooled cabin and results in the increase of energy consumption with the compressor operating for a longer time.

[0003] Various embodiments developed to minimize the effect of the refrigerant migration are explained in various state-of-the-art documents.

[0004] One of these documents is the European Patent Application no. EP0692687. In this application, the prevention of refrigerant migration by using a solenoid valve situated at the inlet of the capillary tube that is regulated by a control unit is explained.

[0005] Another state-of-the-art document is the International Patent Application no.

WO2005088212. In this application, the description is given for the prevention of refrigerant migration and also the elimination of the compressor start-up problem.

[0006] In implementations wherein refrigerant migration is prevented, the evaporator stays dry since it is not filled up with the refrigerant. At the start of the compressor on period, a certain time period passes for the refrigerant to fill up the evaporator and fill to the evaporation temperature along the entire evaporator. This process, called the redistribution of charge in the evaporator (the evaporator filling up with the refrigerant), results in the decrease of the evaporator efficiency and lowering of its cooling capacity during this time period. Even if prevention of the refrigerant migration provides a reduction in energy consumption to a certain extent, the evaporator refilling up with the refrigerant takes a longer time since the evaporator stays entirely dry during the off period.

[0007] The object of the present invention is the realization of a cooling device wherein the evaporator is provided to be refilled with the refrigerant at the start of the next compressor on period while the refrigerant migration effect is reduced.

[0008] The cooling device realized in order to fulfill the objectives of the present invention, explicated in the first claim and the dependent claims thereof, comprises preferably a bi-solenoid valve, situated between the condenser and the expansion element, that prevents refrigerant flow from the condenser to the evaporator by means of the capillary tube that is used as an expansion element during the off -period of the compressor by staying closed and another expansion element, one end of which is connected to this valve and the other end to the evaporator passages between the evaporator inlet and outlet, preferably to a passage near the last passage and a valve between the point wherein this expansion element is connected to the evaporator and the first passages of the evaporator.

[0009] The valve situated between the evaporator passages stays open during the on-period of the compressor providing the refrigerant to flow along the evaporator, and is kept in the closed position during the off period of the compressor, preventing the refrigerant that reaches the evaporator by means of the additional expansion element due to refrigerant migration from reaching the first passages of the evaporator and provides the refrigerant to be directed only to the last passages of the evaporator.

[0010] Accordingly, the refrigerant flowing due to the refrigerant migration effect by means of the capillary tube from the condenser to the evaporator during the off period of the compressor, is directed to the last passages of the evaporator with the additional expansion element and the heating effect resulting from the refrigerant migration is decreased. In order to decrease the effect of refrigerant migration, the directing of the refrigerant migration instead of completely preventing it, also assists in enhancing the redistribution process of the refrigerant at the same time.

[0011] In another embodiment of the present invention, the valve between the evaporator passages is opened by the control unit before the compressor starts its on period and the refrigerant is provided to be distributed in the entire evaporator before the compressor starts its on period. Accordingly pressure is balanced in all of the evaporator passages by opening the valve a short while before the compressor on period starts.

[0012] In yet another embodiment of the present invention, the valve is switched to the open position by the control unit, delaying to change the position of the other valve at the start of the compressor on period and the refrigerant is delivered to the evaporator over the additional expansion element for a certain time period. Accordingly, the process of the refrigerant refilling the evaporator is enhanced by continuing the refrigerant flow over the additional expansion element for a certain time period

[0013] By means of the present invention, in a cooling system operating with an on/off cycle, by decreasing the heating effect of the refrigerant migration that occurs during the off period of the compressor, a more homogeneous distribution of temperature inside the cabin is provided, and at the start of the next on period, enhancement of the refilling of refrigerant into the evaporator is provided as compared to implementations wherein refrigerant migration is completely prevented.

[0014] The cooling device realized in order to fulfill the objectives of the present invention is illustrated in the attached figures, where:

[0015] Rgure 1 - is the general view of the cooling device.

[0016] Rgure 2 - is the schematic view of an embodiment of the cooling system of the cooling device of the present invention.

[0017] The elements shown in figures are numbered as follows:

1. Cooling device

2. Compressor

3. Condenser

4. Expansion element

5. Evaporator

6. , 16. Valve

7. Additional expansion element

8. Control unit

[0018] The cooling device (1) of the present invention comprises a compressor (2) that provides compression of the refrigerant, a condenser (3) providing the refrigerant leaving the compressor (2) as overheated vapor to be condensed to change first to the lquid- vapor phase and then to the lquid phase completely, one or more evaporators (5) providing to cool the ambient environment by the refrigerant circulating within absorbing heat, an expansion element (4) providing the refrigerant leaving the condenser (3) to expand and to be delivered to the evaporator (5), preferably a bistable solenoid valve (6) situated between the condenser (3) and the expansion element (4) that shuts off the refrigerant flow from the condenser (3) to the evaporator (5) during the off period of the compressor (2) (Rgure 1).

[0019] The cooling device (1) comprises an additional expansion element (7) with one end extending to the valve (6) and the other end into between the evaporator (5) passages, providing to direct the refrigerant migration to a portion of the evaporator (5), a second valve (16) separating the evaporator (5) into two by being situated between the evaporator (5) inlet and the point wherein the additional expansion element (7) is connected to the evaporator (5), and a control unit (8) that provides the refrigerant to reach from the condenser (3) to the evaporator (5) and to the compressor (2) by means of the first valve (6) and by way of the expansion element (4) thus completing the cooling cycle by opening the second valve (16) while the compressor (2) operates and when the compressor (2) stops, closing the second valve (16) providing the refrigerant that tends to flow from the condenser (3) to the evaporator (5) by the first valve (6) due to the refrigerant migration effect, to be directed over the additional expansion element (7) to the passages of the evaporator (5) situated after the second valve (16) and to bypass the evaporator (5) passages between the two valves ( 16 and 6) (Rgure 2).

[0020] The additional expansion element (7) is selected to be with a lesser resistance than the expansion element (4), that is of a greater diameter, with a shorter length in order to cause a smaller pressure decrease of the refrigerant.

[0021] The valve (6) is a bi-stable solenoid valve with one inlet port- two outlet ports, the inlet port extending to the condenser (3), one of the outlet ports extending to the expansion element (6), and the other to the additional expansion element (7).

[0022] In this embodiment of the present invention, the control unit (8) regulates the valves (6,16) with a control method in the following way: During the on period of the compressor (2), the port of the valve (6) between the expansion element (4) and the condenser (3) extending to the expansion element (4) is open, the port extending to the additional expansion element (7) is closed and the refrigerant is allowed to reach the expansion element (4) but not to the additional expansion element (7). In this case the second valve (16) is in the open position. The refrigerant reaching the condenser (3) by flowing from the discharge line, passes from the condenser (3) to the evaporator (5) by way of the expansion element (4) and reaches the compressor (2) again from the suction line. When the compressor (2) stops, the position of the valve (6) is changed by the control unit (8) and its port extending to the expansion element (4) is closed, the port extending to the additional expansion element (7) is opened. Simultaneously, the other valve (16) is changed to the closed position by the control unit (8). In this case the refrigerant that tends to flow from the condenser (3) to the evaporator (5) due to the refrigerant migration effect, reaches the evaporator (5) over the additional expansion element (7) because the port of the valve (6) extending to the expansion element (4) is closed, and the passages of the evaporator (5) between the valve (16) situated at the point wherein the additional expansion element (7) is connected to the evaporator (5) and the compressor (2) are filled up with the refrigerant until the pressure between the suction and discharge lines is balanced. When the pressure between the compressor (2) suction and discharge lines is balanced, the effect of the refrigerant migration is entirely over. As the on period of the compressor (2) starts, the valves (6 and 16) are changed to their initial positions, directing the refrigerant flow leaving the condenser

(3) to the expansion element (4).

[0023] In the control method implemented by the control unit (8) in another embodiment of the present invention, the valve (16) between the evaporator (5) passages is opened before the compressor (2) starts its on period, and the distribution of the refrigerant to the entire evaporator (5) is provided before the compressor (2) starts its on period. In this embodiment, since the refrigerant migration loses its heating effect after the first moments of the compressor (2) off period, the valve (16) is opened a short while before the on period starts, providing to balance the pressure between all of the evaporator (5) passages. With the start of the on period, the position of the valve (16) is changed and the refrigerant leaving the condenser (3) is directed to the expansion element (4). Directing the refrigerant to the passages of the evaporator (5) between the valve (16) and the compressor (2) without preventing refrigerant migration, prevents the increase of temperature differences in the cooling cabin that results in a homogeneous distribution of temperature within the cabin. Furthermore, the redistribution of the refrigerant is enhanced as compared to the case when refrigerant migration is prevented.

[0024] In another embodiment of the present invention, the valve (16) is changed to the open position by the control unit (8), delaying the change of position of the valve (6) at the start of the compressor (2) on period and the refrigerant is delivered to the evaporator (5) over the additional expansion element (7) for a certain time period.

[0025] In this embodiment, the process of the evaporator (5) filling up with the refrigerant is enhanced by continuing the refrigerant flow over the additional expansion element (7) for a certain time period. Since the additional expansion element (7) with a lower resistance functions in the first moments of the compressor (2) on period, all of the evaporator (5) passages up to the evaporator (5) outlet can be wetted in a short while. After this time period the refrigerant flow is again directed over the expansion element

(4) by opening the valve (6).

[0026] By way of the present invention, refrigerant migration is not prevented altogether; instead, it is directed to a portion of the evaporator (5). In an on /off operating cooling system, a more homogeneous distribution of temperature within the cabin is provided by decreasing the heating effect of the refrigerant migration that occurs during the compressor (2) off period, enhancing the refilling up of the evaporator (5) with refrigerant at the start of the next on period.

Claims

[0001] A cooling device (1) comprising a compressor (2) that provides compression of the refrigerant, a condenser (3) providing the refrigerant leaving the compressor (2) as overheated vapor to be condensed to pass first to the liquid- vapor phase and then to the liquid phase completely, one or more evaporators (5) providing to cool the ambient environment with the absorption of heat by the refrigerant circulating within, an expansion element (4) providing the refrigerant leaving the condenser (3) to expand and to be delivered to the evaporator (5), a valve (6) situated between the condenser (3) and the expansion element (4) that shute off refrigerant flow from the condenser (3) towards the evaporator (5) during the off period of the compressor (2) and characterized by an additional expansion element (7) with one end extending to the valve (6) and the other end in between the evaporator (5) passages, providing to direct the refrigerant migration to a portion of the evaporator (5), a second valve (16) separating the evaporator (5) into two by being situated between the evaporator (5) inlet and the point wherein the additional expansion element (7) is connected to the evaporator (5), and a control unit (8) -that provides the refrigerant to reach from the condenser (3) to the evaporator (5) and to the compressor (2) by means of the first valve (6) and by way of the expansion element (4) thus completing the cooling cycle by opening the second valve (16) while the compressor (2) operates, -and when the compressor (2) stops, closing the second valve (16) providing the refrigerant that tends to flow from the condenser (3) to the evaporator (5) by the first valve (6) due to refrigerant migration effect, to be directed over the additional expansion element (7) to the passages of the evaporator (5) situated after the second valve (16) and to by-pass the evaporator (5) passages situated between the two valves ( 16 and 6).

[0002] A cooling device (1) as in Claim 1, characterized by an additional expansion element (7) that is selected of a greater diameter, with a shorter length than the expansion element (4), such that it will cause a smaller pressure decrease of the refrigerant.

[0003] A cooling device (1) as in Claim 1, characterized by a control unit (8) that opens the valve (16) between the evaporator (5) passages before the compressor (2) slarte ite on period, and provides the distribution of the refrigerant to the entire evaporator (5) before the compressor (2) slarts ite on period. A cooling device (1) as in Claim 1, characterized by a control unit (8) that changes the valve (16) between the evaporator (5) passages to the open position and delays change of position of the valve (6) at the start of the compressor (2) on period and provides the delivery of the refrigerant to the evaporator (5) over the additional expansion element (7) for a certain time period.