R744 (CO₂) Refrigerant Cooling Systems, the Finned Tube R744 (CO₂) Evaporator and Gas Cooler Design Principles

R744 (CO₂) was used in the early stages of the refrigeration industry, but it lost the competition with halocarbon refrigerants because of its high operating pressure and the loss of capacity and coefficient of performance when rejecting heat near or above the critical point. Because the negative effect of halocarbon refrigerants on environment, that R744 started to used recently. New heat exchanger technology and system components allow R744 to reach competitive efficiency levels for transcritic cycle especially in northern countries and for sub-critic cascade cycle in southern countries.

Recently, CO₂ has been increasingly studied for application as the primary refrigerant in transcritical mobile air conditioners, vending machines, supermarkets, cold rooms, food production and process industry, industrial ice cream machineries and heat pumps.

This article is prepared to give general technical information on R744 cooling systems, CO₂ evaporators and gas coolers.