A METHOD AND ARRANGEMENT FOR SIMULATING FAN SHUTTERING

Abstract: When defrosting a refrigeration battery of a refrigeration compartment in a closed insulating transport container, the battery is heated subsequent to interrupting the supply of refrigerant thereto for vaporization thereby. In order to shorten the time taken to defrost the batteries, while obtaining a more reliable defrosting operation without needing to use mechanical fan shutters, there is proposed a method and an arrangement for simulated fan shuttering functions, in which the fans delivering air to the refrigeration battery are operated over short time periods during the actual defrosting process. The warm air is blown repeatedly by the fans through the refrigeration battery and is forced repeatedly back therethrough, such that the heated air flows backwards and forwards through the battery in a manner to achieve improved defrosting of the battery without appreciably influencing the temperature in the refrigeration compartment.

Description: A METHOD AND ARRANGEMENT FOR SIMULATING FAN SHUTTERING DESCRIPTION Technical Field The present invention relates to a method and to an arrangement for simulating the shuttering of fans when defrosting refrigerating batteries, for example when defrosting refrigerating batteries which generate re¬ frigeration air in the refrigeration compartment of a closed, insulated transport container. Background Art When defrosting a refrigeration battery of a refrigera¬ tion compartment in a closed, insulated transport con¬ tainer, the refrigeration battery is heated subseguent to interrupting the supply of refrigerant for vapouriza- tion in the system evaporator. In order to prevent the heated air from leaving the refrigeration battery and continuing into the refrigeration compartment, a fan shuttering device may be mounted in connection with the fan used to generate the flow of cold air during refrig¬ eration. The fan shuttering device may, for instance, consist of thin metal plates or shutters which function to close the fan openings on the refrigerator side when the fan is switched off and thus stationary. The con- struction of mechanical fan shuttering devices often exhibits limitations in the form of unreliable shutter¬ ing functions. Disclosure of the Invention With the intention of shortening the time.taken to defrost refrigerating batteries and, at the same time, to achieve greater reliability in the actual defrosting of said batteries without needing to use mechanical fan shutters, there is proposed a method and an arrangement for simulating a fan shutter function in which the fans which direct warm air onto the refrigeration battery are operated over short time periods during the actual defrosting operation. The warm air formed when defrost¬ ing the battery rises and collects above the refrigera- tor. This warm air is blown repeatedly downwards by the fans and is pressed back, through the refrigeration battery during said short time periods, the heated air moving forwards and backwards through said battery so as to improve defrosting of said battery without influenc- ing the temperature in the refrigeration compartment to any appreciable extent. Water and ice flakes loosely seated on the refrigeration battery surfaces are thrown from the battery and do not consume energy during con¬ tinued defrosting of the battery. Brief Description of the Drawing The single Figure of the accompanying drawing is a simple illustration of a closed insulated cargo contain- er equipped with a control unit and a refrigerating plant. Best Mode of Carrying Out the Invention The Figure is a simple illustration of the construction of an insulated transport container 1 having a refrig¬ eration compartment 2 and a refrigeration unit 3, 4. The refrigeration compartment 2 is cooled by blowing cold air through the refrigeration compartment 2 by means of a fan, said air being cooled in a refrigeration battery 3. Cooling of the refrigeration .compartment is effected by passing cooled or chilled air into the compartment through inlet openings 5 provided in the compartment floor and exiting said air through exhaust openings 6 provided at the top of one end wall of the compartment. Cooled air is caused to pass through the refrigeration compartment during said cooling process. The refrigeration units 3, 4 are placed on one side of the refrigeration compartment 2 in the insulated cargo container 1 and consist of one or more electric fans 4 and a refrigeration battery 3. The refrigeration bat¬ tery 3 is connected to an external refrigeration plant 7, which supplies the battery 3 with coolant. Defrost¬ ing of the refrigeration battery 3 can be effected with hot gas taken from the refrigeration plant 7 and caused to flow through the battery 3, said battery then func¬ tioning as a condenser. Alternatively, the battery 3 may be heated electrically during the defrosting pro¬ cess. An external control unit 8 is connected to the external refrigeration plant 7 which coacts with the battery 3 , and also to the electrically operated fan 4. The values of prevailing system state parameters, such as the real values prevailing in the refrigeration compartment, are delivered to the external control unit by a measuring device 9 and are there processed and compared with the set point values of said parameters stored in the exter¬ nal control unit, which then adjusts the flow of refrig¬ erant in response to a prevailing refrigerant require- ment. The external control unit 8 is thus able to initiate defrosting of the battery. The unit first interrupts the delivery of liquid refrigerant to the refrigeration battery, which in normal refrigerating conditions functions as an evaporator. The battery 3 is then heated electrically over a time period T_ . Alter¬ natively, the battery may be heated by passing "hot gas", hot gaseous refrigerant, through the battery 3 over said time period. As the battery is heated, warm air will be formed and collected in a space 10 above the battery 3. The warm air rises up through a fan opening 11 and up into a cooling space 12. Upon termination of the time period T x , the fan 4 is again run for a short period. The warm air in the cooling space 3 and in the space above the battery is then moved back through the battery 3 and fills a cavity 13 located beneath said battery. This backflow of air will cause loose ice flakes and water to be blown from the battery. When the fan 4 is stopped, heating of the battery 3 for defrost¬ ing pur-poses is continued over a time period T 2 and the air is transported back to the refrigeration battery and to the space 10 above said battery and to the space 12 above said fan through the chimney effect created. Subsequent to termination of the time period T 2 , the fan 4 is again started-up for a brief moment, causing the warm air above the battery to be again forced back through said battery. The procedure of heating the battery and running the fan for short time periods is continued until the battery is completely defrosted. During defrosting of the battery, which may take from 60 to 80 minutes, the fans may be driven for 2-3 seconds on each said occasion and the duration of the fan driving times (T l T 2 ...) may vary between 5 and 15 minutes at a constant- or decreasing fan.speed. When practicing the invention method, the air that has been heated in the refrigeration battery does not disap¬ pear into the cargo space, but is moved backwards and forwards through the refrigerator. Water and ice flakes which sit loosely on the refrigerator surfaces are thrown from the refrigerator and do not consume energy during continued defrosting of the battery. The tem¬ perature of the air beneath the battery can be accurately determined upon completion of a defrosting operation.

Claims: CLAIMS 1. A method for simulating a fan shuttering function when defrosting a refrigeration battery or the like in- stalled, for instance, in a refrigeration compartment of a closed, insulated transport container, c h a r a c ¬ t e r i z e d in that defrosting is effected by operat¬ ing one or more fans {4) over short time periods while heating the refrigeration battery (3) at the same time, causing heated air to be blown down and pressed through the battery (3) repeatedly such as to cause said heated air to move backwards and forwards through said battery (3) while defrosting said battery without appreciably influencing the temperature of the refrigeration com- partment (2). 2. An arrangement for simulating a fan shuttering func¬ tion when defrosting a refrigeration battery or the like, e.g. the refrigeration battery of a refrigeration compartment in a closed, insulated transport container, c h a r a c t e r i z e d in that for the purpose of defrosting said battery (3) , one or more fans (4) are arranged in connection with the cooling battery and are operated for short time periods such that heated air will be blown down and pressed through said battery; and in that the arrangement includes an external control unit (8) which, together with an external refrigeration plant (7), functions to. ensure that the delivery of refrigerant to the refrigeration battery (3) is inter- rupted and that the battery is heated during defrosting of said battery. 3. An arrangement for simulating a fan shuttering function when defrosting a refrigeration battery in accordance with Claim 2, c h a r a c t e r i z e d in that the external control unit (8) is intended to ensure that the fan or fans (4) is/are operated over short time periods during heating of the battery; and in that the time intervals (T., T 2 ...) may be constant, varying or decreasing respectively.

Inventors: MARTINSON ANDERS, OLESZKO JACEK, MARTINSON, ANDERS, OLESZKO, JACEK
Applicants: STAL REFRIGERATION AB
Application year: 1991
Main classification: F25D21
IPC codes: F25D11, F25D21