NUMERICAL ASSESSMENT OF EFFICIENCY IMPROVEMENT BY IMPLEMENTATION OF A CONTROL TECHNIQUE IN TRANSCRITICAL CO_2 AIR CONDITIONING SYSTEMS

摘要

An optimum pressure that maximizes the COP exists for vapor compression cycles where heat rejectionrnoccurs under supercritical pressure, e.g. CO_2 transcritical cycles. The paper presents a performancerncomparison between two transcritical split air conditioning units operating under typical subtropicalrnconditions of Pune city (India). First system of comparison has a control technique to set the gascoolerrnpressure to its optimum value while second system does not have such a control. The comparison hasrnbeen carried out by numerical simulations as function of indoor and outdoor conditions. The parametersrnanalyzed are the COP improvement and power input reduction by using a control procedure. The resultsrnrevealed COP improvements up to 15% and power reductions at most of 22%. The operating conditionsrnto find the largest improvement correspond to large indoor humidity and low outdoor temperature.