Benchmarking models for the ongoing commissioning of heat recovery process in a central heating and cooling plant

This paper presents the development of benchmarking models for the ongoing commissioning of heat recovery process in a cooling and heating plant that provides chilled water and heating water to HVAC (heating, ventilation and air conditioning) systems on a university campus. The heat recovered from the chillers in the summer was used for the heating water loop. The proposed ongoing commissioning approach and GUI (graphical user interface) are presented. The benchmarks were developed using measurements from the BAS (Building Automation System). The results indicated that the performance indices should be analyzed at both levels: the heat exchanger and the whole heat recovery system. Although the heat exchanger (HX3) effectiveness was reduced from an average value of 0.85 in 2008 to 0.60 in 2010, the effectiveness was greater than the benchmarks limits of 0.13-0.15. That reduction did not translate into a significantly lower performance of the whole heat recovery system. The BAS was able to control the system adaptation to this degradation of performance of HX3, by increasing the heating water flow rate, with an increase of electric power of pumps of only 6%. As a result, additional heat input to the system was never required. The whole heat recovery system works within the benchmarking limits.