Dynamic Heat Process in a Climate Chamber

Abstract: Heat pumping technology is commonly used for heating and cooling purposeswithin building services nowadays. It has quick response for improving the indoorclimate with high heat to power ratio. SP' was the first accredited Europeaninstitute for heat pump performace testing with a focus on measuring theCoefficient of Performance (COP). The testing is commonly performed byinstalling the heat pump in a climate chamber which can provide standard testingconditions.In the energy technology department of SP there is a new climate chamber thathas recently been used in a research project to evaluate the performance of twoair-to-air heat pumps. The performance of the climate chamber is critical to theaccuracy of the testing results. The objective of this study is to determine thethermal property of the climate chamber, develop a numerical model to describethe dynamic thermal process of the chamber and evaluate the testing results bysimulating the heating process.By transforming the chamber thermal model to an equivalent analog electricalcircuit and solving this first order system, an equation set was derived to describethe chamber thermal process. Several measurements and computer calculationswere performed to determine the optimal parameters for the model. Finally themodel was integrated with Matlab GUI and developed as a programme with userinterface.Several heat pump testing cases were investigated with this model. The resultsshow that for measurements without large power variation and defrosting cyclesthe COP values from the Calorimeter test method and the simulations are veryclose. However, for measurements with large power variation or defrosting cyclesthere is a difference between these two results. This is mainly derives from thedynamic heat process where heat storage and heat loss influence the heat balancecalculation. For defrosting process, the model can recreate the heating capacitiesreflecting real heat pump running condition.Another utilization of the model is to analyze upgrade scenarios of the climatechamber. The chamber size is the most critical factor and should be kept smallbesides the necessary operation space. An increase of the thickness of the insulationlayer can also improve the testing quality.Further effort is suggested to expand the model to other climate chambers and realbuildings. By combining the model with climate control systems, it could alsoimprove the control quality of the climate chamber.