Transport refrigeration system and method of operation

Inactive Publication Date: 2011-03-03
CARRIER CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]By yet another aspect of the invention, control methods and apparatus are provided to prevent the digital scroll compressor from becoming overloaded in such a system.

Problems solved by technology

Transport refrigeration systems, such as those used in trucks / trailers and refrigerated containers, operate in very unpredictable environments.
Also the product load may vary dramatically and in unpredictable manner.
While such a so called “digital scroll compressor” has been implemented primarily for use in residential air conditioning systems operating in a subcritical condition, it has not been applied to transport refrigeration systems operating in a transcritical cycle.
The primary reason for this is that such a digital scroll compressor is not capable of operating for prolonged periods of time under conditions of the high pressure ratios that are necessary for the efficient operation in the transcritical range.
Further, the transportation refrigeration system is characterized by extremely tight temperature control requirements.
In perishable part load operating conditions, it results in very low mass flow rate.
A large amount of liquid injection has to be used in order to keep the compressor discharge temperature within the operating limit such as 275° F. Under low mass flow rate, when liquid injection exceeds a certain amount, the suction superheat will become so low that it is possible to damage a compressor with liquid flooding.
So the challenge is to design a system which can operate with low mass flow rate yet, have its compressor discharge temperature still within a safe limit

Method used

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  • Transport refrigeration system and method of operation
  • Transport refrigeration system and method of operation
  • Transport refrigeration system and method of operation

Examples

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Embodiment Construction

[0015]The invention is shown generally at 10 as incorporated into a refrigerant vapor compression system operating with CO2 as the refrigerant and having in serial flow relationship, a compressor 11, a refrigerant heat rejecting heat exchanger 12, an expansion device 13 and a refrigerant heat absorbing heat exchanger 14. The refrigerant heat absorbing heat exchanger 14, commonly referred to as an evaporator, includes a motor driven fan 16 for circulating air thereover so as to be cooled.

[0016]Since the system uses CO2 as the working fluid, it necessarily operates in a transcritical cycle, such that the refrigerant heat rejecting heat exchanger 12, which may be referred to as a condenser, has high pressure refrigerant passing in heat exchange relationship with a cooling medium, most commonly ambient air, in air conditioning systems or transport refrigeration system. In such a refrigerant vapor compression system operating in a transcritical cycle, the refrigerant heat rejecting heat ...

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Abstract

A refrigerant vapor compression system using CO2 as the working fluid and operating in a transcritical cycle, compression of the refrigerant is accomplished by use of a digital scroll compressor adapted to a variable duty cycle in a pulse width modulation manner. The compression ratio is maintained at an acceptable level by selective control of various components within the system, depending on the mode of operation.

Description

TECHNICAL FIELD[0001]This invention relates generally to transport refrigeration systems and, more particularly, to capacity modulation in a refrigerant vapor compression system operating in a transcritical cycle.BACKGROUND OF THE INVENTION[0002]Refrigerant vapor compression systems are well known in the art and commonly used for conditioning air to be supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigerant vapor compression systems are also commonly used in transport refrigeration systems for refrigerating air supplied to a temperature controlled cargo space of a truck, trailer, container or the like for transporting perishable items. Traditionally, most of these refrigerant vapor compression systems operate at subcritical refrigerant pressures and typically include a compressor, a condenser, and an evaporator, and expansion device, commonly an expansion valve, disposed upstream, with respect to ...

Claims

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Application Information

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IPC IPC(8): F25B1/00F25D17/00
CPCF25B9/008F25B49/02F25B49/022F25B49/027F25B2309/061F25B2400/13F25B2400/23F25B2600/025F25B2600/0251F25B2600/111F25B2700/19F25B2700/1931F25B2700/2104F25B2700/21152B60H1/3216B60H2001/3292F25B31/008F25B41/39
InventorCHEN, YU H.LIU, LUCY YI
OwnerCARRIER CORP