Gas cooler with reduced pipe to pipe heat conduction.

It is suggested how to optimise the coil design for a CO2 gas cooler in a 9kW condensing unit (CDU) for medium temperature (MT) applications by avoiding heat transfer from pipe to pipe. Air cooled gas coolers for CO2 with coils of copper tubes and aluminium fins are often designed as condensers for traditional refrigerants. The heat transferred via the fins from pipe to pipe is often neglected. This constitutes a loss which is bigger for trans critical CO2 applications than for other refrigerants. A method is described which uses a simple guideline for the layout of the circuitry and checks the performance by means of calculations consistent with the ecodesign requirements for CDUs. The calculations of the coils are carried out by a freeware calculation program. It is expected that the new design can improve the seasonal energy performance ratio (SEPR) by up to 8%. Tests are pending to verify the design.