REFRIGERATION CYCLE
In a refrigeration cycle comprising a compressor, a condenser, a pressure reduction and expansion means, and an evaporator, R1234yf is used as the refrigerant, the refrigerant at the exit side of the evaporator is controlled in a superheated condition, and the refrigeration cycle is operated in a range of 5 to 16 degrees of superheat, and preferably in a range of 10 to 16 degrees of superheat. When the refrigerant used is changed to the new refrigerant R1234yf, while high advantage for improving the coefficient of performance can be achieved, the rise in temperature of the discharged refrigerant is appropriately suppressed so that deterioration of refrigerating machine oil in the refrigerant can be prevented, and a high-efficiency operation can be realized as the entirety of the refrigeration cycle.
The present invention relates to a refrigeration cycle, and specifically relates to a refrigeration cycle which can be efficiently operated when a specific new-type refrigerant is used.
BACKGROUND ART OF THE INVENTIONA refrigeration cycle used in an automotive air conditioning system, etc., has basic configuration which is shown in
For example, where sample 11 of operating condition of refrigeration cycle 1 is shown in the Mollier diagram (enthalpy/pressure curve) of
Characteristics as shown in
R134a is a refrigerant which is typical at present, however, research and development to find a new-type refrigerant are being performed in order to improve Global Warming Potential (GWP), as disclosed in non-patent document 1. R1234yf has been announced recently as a new refrigerant aiming at such an improvement, and it is becoming possible that it is examined and studied for applying to refrigeration cycle used for an automotive air conditioning system, etc.
PRIOR ART DOCUMENTS Non-Patent DocumentsNon-patent document 1: Refrigeration, Vol. 83, No. 965, March issue, 2008
SUMMARY OF THE INVENTION Problems to be solved by the InventionAt present when R134a is used as refrigerant, the refrigerant condition is generally controlled around 5 superheat degrees at the outlet side of the evaporator, and the operation, regardless of high load and low load, is performed in a condition around 5 degrees superheat. Such a condition of 5 degrees superheat has been configured for the following reasons. (1) The condition of 5 superheat degrees is regarded as being close to the requisite minimum to achieve a target refrigeration gasification state at the outlet side of the evaporator. (2) If the condition is set as substantially higher than 5 degrees superheat, the temperature of refrigerant discharged from the evaporator might exceed a certain level as causing deterioration of refrigerant oil contained in the refrigerant.
However, because specific enthalpy difference of R1234yf in an operating zone is less than that of R134a, refrigerant flow rate for an operation using R1234yf has to be increased to achieve a refrigeration performance same as that for an operation using R134a as a conventional refrigerant. In order to achieve the same refrigeration performance in refrigeration cycle 1 with basic configuration as shown in
According to the above-described new knowledge, an object of the present invention is to provide a refrigeration cycle which can be operated with a high efficiency even if the refrigerant has been replaced with R1234yf as new-type refrigerant.
Means for solving the ProblemsTo achieve the above-described object, a refrigeration cycle according to the present invention is a refrigeration cycle comprising a compressor for compressing refrigerant, a condenser for condensing compressed refrigerant, a pressure reduction and expansion means for reducing in pressure and expanding condensed refrigerant, and an evaporator for evaporating pressure-reduced and expanded refrigerant, characterized in that R1234yf is used as refrigerant for the refrigeration cycle, and the refrigeration cycle is operated so that the refrigerant at an exit side of the evaporator is controlled in a superheated condition, and the superheated condition is controlled in a range of 5 to 16 degrees of superheat.
In other words, it is characterized in that conventional operating condition around 5 superheat degrees in a case using R134a as refrigerant so as to keep the refrigerant superheated at the exit side of the evaporator has been changed to an operating condition between 5 and 16 superheat degrees, when the refrigerant has been replaced with R1234yf as a new-type refrigerant so as to keep the refrigerant superheated at the exit side of the evaporator. As shown in
The refrigeration cycle according to the present invention may be operated at 5-16 superheat degrees of refrigerant at the exit side of the evaporator, and more preferably, is operated at in a range of 10-16 superheat degrees thereof as keeping the superheat degree as high as possible, in order to achieve the deterioration prevention of the refrigerant oil by suppressing the discharged refrigerant temperature rise. Namely, if attention is focused on the discharged refrigerant temperature shown in
In addition, the refrigeration cycle according to the present invention, whose basic configuration is shown in
Such a refrigeration cycle according to the present invention is basically applicable to any refrigeration cycle which aims to use the new-type refrigerant R1234yf, and is specifically suitable to a refrigeration cycle used in an automotive air conditioning system which is required to achieve efficient operation and to be highly durable for a long term by preventing the refrigerant oil from deterioration.
EFFECT ACCORDING TO THE INVENTIONThe refrigeration cycle according to the present invention makes it possible that when the refrigerant is replaced to the new-type refrigerant R1234yf, the improvement of coefficient of performance (COP) can be greatly achieved and the discharged refrigerant temperature can be properly kept from rising as preventing from the deterioration of the refrigerant oil in refrigerant, so that refrigeration cycle can be operated efficiently as a whole.
Hereinafter, the present invention will be explained as referring to figures as well as embodiments of the present invention.
The basic configuration of equipments provided in a refrigeration cycle of the present invention can be the one as shown in
The characteristics comparison between R134a and R1234yf in
The refrigeration cycle according to the present invention is applicable to any refrigeration cycle, and specifically, is suitable as a refrigeration cycle used in an automotive air conditioning system.
EXPLANATION OF SYMBOLS
- 1: refrigeration cycle
- 2: compressor
- 3: condenser
- 4: expansion valve as pressure-reduction/expansion means
- 5: evaporator
- 11: sample of operating condition of refrigeration cycle
- 12: compression process
- 13: saturation curve
- 14: superheat degree
- 15: isentrope
- 16: isotemperature line
Claims
1. A refrigeration cycle comprising a compressor for compressing refrigerant, a condenser for condensing compressed refrigerant, a pressure reduction and expansion means for reducing in pressure and expanding condensed refrigerant, and an evaporator for evaporating pressure-reduced and expanded refrigerant, characterized in that R1234yf is used as refrigerant for said refrigeration cycle, and said refrigeration cycle is operated so that said refrigerant at an exit side of said evaporator is controlled in a superheated condition, and said superheated condition is controlled in a range of 5 to 16 degrees of superheat.
2. The refrigeration cycle according to claim 1, wherein said refrigeration cycle is operated at said superheated condition in a range of 10 to 16 degrees of superheat of said refrigerant at said exit side of said evaporator.
3. The refrigeration cycle according to claim 1, wherein said refrigeration cycle comprises means for elevating said degree of superheat of said refrigerant at said exit side of said evaporator, as compared with a case where R134a is used as refrigerant for said refrigeration cycle.
4. The refrigeration cycle according to claim 1, wherein said refrigeration cycle is used in an air conditioning system for vehicles.
Type: Application
Filed: Apr 27, 2009
Publication Date: Mar 10, 2011
Inventor: Yuuichi Matsumoto (Gunma)
Application Number: 12/991,683
International Classification: F25B 1/00 (20060101);