Direct CO2-ground condensers

Abstract

The utilization of a direct condensing CO2 ground heat exchanger as an auxiliary heat rejection device for commercial or industrial refrigeration applications offers several advantages. During the cold season, and especially when periods with frost and snow occur, the heat can be utilized to keep roadways safe. During the summer, the ground temperature is lower than the ambient temperature during the hottest hours of a day, i.e. the heat rejection can be performed successively: first towards the ambient air and thereafter towards the ground. Many retail stores and distribution halls find it necessary to install snow melting devices in the ground below the area where trucks are loaded. They also install large condensers on the roof for rejecting surplus heat from the refrigeration system. To reduce installation costs and enhance energy efficiency, the two needs should be combined, and the heating performed directly via ground heat exchangers instead of implementing indirect systems as is often the case today. However, it is important to ensure safety and sufficient heat transfer for the concept to be applicable. It is found that this requires i.a. seamless pipes without welding joints in the ground, segmentation of the heat transfer area, service trenches and smart control.