Performance of a Masterflux Compressor in a Refrigeration Unit for High End Computer System Application

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. Challenge has been to limit the rise in chip temperature above the ambient. In the past, virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. Until recently large scale scientific computers used direct immersion cooling of SCM’s. The current research focuses on mainframe (computer system), which uses conventional system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Multivariable control of compressor speed along with Thermostatic expansion valve opening can give better stability performance. Compressor is the only mechanical-working component in the Refrigeration cycle that circulates refrigerant through the system in a continuous cycle. Hence, the role of a compressor in the unit is significant and should be carefully studied. The control objective is defined as improving the transient behavior of the vapor compression cycle for the Refrigeration System around operating an evaporator set point temperature. The control system can give the better performance stability in regulating Evaporator Temperature. Also the interface temperature (temperature between the evaporator and heat dissipation device) should be maintained within a tolerance range. In this paper, first, the characteristics of the thermostatic expansion valve with the Masterflux compressor, the effect of variation of evaporator outlet superheat on the flow through the TXV at varying evaporator temperature, and effect of sudden changes in evaporator heat load and condenser pressure variation on the temperature oscillations at the evaporator is examined to determine the appropriateness of the compressor for such an application. Once that has been determined, the effect of Multivariable controlled compressor speed working with TXV and the advantages it offers regarding the steadiness of the unit will be reported.