Refrigeration – Processes – Compressing – condensing and evaporating
Reexamination Certificate
2000-07-26
2001-10-09
Tapolcai, William E. (Department: 3744)
Refrigeration
Processes
Compressing, condensing and evaporating
C062S498000
Reexamination Certificate
active
06298674
ABSTRACT:
The invention relates to a method for operating a subcritically and transcritically operated vehicle air conditioner.
BACKGROUND
DE 4432272 C2 describes a method for operating a refrigerating apparatus for air conditioning vehicles. The vapour compression circuit has at least in each case one compressor, one gas cooler, one throttling means and one evaporator. The refrigerating capacity is regulated by a compressor which controls the refrigerant mass flow. The refrigeration efficiency is a function of high pressure in the case of supercritical heat output at the gas cooler. The desired high pressure is set by means of an expansion valve.
EP 0 424 474 B1 describes a method for transcritical and supercritical operation of a vapour compression circuit. The air-conditioning circuit has a compressor, a cooler, throttling means and an evaporator. The refrigeration efficiency is a function of high pressure in the case of supercritical heat output at the cooler. The high pressure is regulated by variation of the refrigerant quantity on the high-pressure side of the circuit.
With this type of operation of a vehicle air conditioner, it is disadvantageous that upon starting up the vehicle air conditioner, the refrigerant mass flow and the high pressure do not immediately rise to the desired value. This is to be ascribed, for example, to the fact that additional pressure drops are produced in the system, and the refrigerant mass distribution in the overall system does riot correspond to the desired distribution. It is particularly disadvantageous when determining the optimum high pressure to use the refrigerant temperature at the gas cooler outlet, since this is itself a function of the high pressure, and thus subjected to incessant fluctuations.
The object of the invention is to improve a vehicle air conditioner so as to permit efficient starting up of the conditioner and efficient and reliable operation of the conditioner.
SUMMARY
A method according to the invention is for operating a subcritically and transcritically operated vehicle air conditioner having a vapour compression circuit in which in which a compressor, a gas cooler, an expansion valve and an evaporator are connected in series and form an integral closed cycle. On the high-pressure side of the vapour compression circuit, for the purpose of offering refrigerating capacity, a pressure is produced which is supercritical with reference to the critical pressure of the refrigerant circulating in the circuit, and a subcritical pressure is reached simultaneously on the low-pressure side of the circuit. Thermal energy is fed via the evaporator to the refrigerant cooled down on the low-pressure side with the refrigerant mass flow being regulated by the compressor and the desired high pressure being set by means of an expansion valve. During the starting operation of the vehicle air conditioner, the refrigerant mass flow is set directly to a required value and the refrigerant pressure is set in accordance with at least one prescribed parameter, and the air conditioner is regulated upon the overshooting of safety pressure limits P
1
-P
4
, the regulation depending upon which safety pressure limits are overshot.
REFERENCES:
patent: 5497631 (1996-03-01), Lorentzen et al.
patent: 5685160 (1997-11-01), Abersfelder et al.
patent: 5901560 (1999-05-01), Heile et al.
Finkenberger Thomas
Kauf Florian
Wertenbach Jurgen
Calcaterra Mark P.
Daimler-Chrysler AG
Tapolcai William E.
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