Experimental study of heat pipe heat exchanger in hospital HVAC system for energy conservation

Abstract-The hospitals Heating, Ventilation, and Air Conditioning (HVAC) systems consumed large amounts of energy due to the specific requirements that must be met to ensure that environmental conditions were healthy, convenient, and safe. Therefore, to reduce electricity consumption without sacrificing comfort and improving indoor air quality, the utilizing of heat pipe heat exchanger (HPHE) is necessary and highly recommended. An experimental study was conducted to investigate the thermal performance of heat pipe in recovering the heat of an exhaust air from a room simulator. HPHE consisted of several tubular heat pipes with water as a working fluid and staggered by up to six rows. The outer diameter of each heat pipe was 13 mm and length of 700 mm with fins mounted on each heat pipe. A series of experiments was conducted to determine the effect of inlet air temperature. The influence of the number of heat pipe rows and air velocity was also investigated. The experiments showed that the higher inlet air temperature, the more effective the HPHE performance became. The cooling capacity of the system had increased. It was indicated by the decrease of air temperature entering the evaporator by 2.4 °C with the effectiveness of 0.15. This result was achieved when using six rows HPHE, air velocity 1 m/s, and evaporator inlet air temperature 45 °C. When air velocity was doubled to 2 m/s, the system reached the largest amount of heat recovered of 1404.29 kJ/hour. The overall use of energy in HVAC system from the annual prediction of heat recovery for 8 h/day and 365 days/year would decrease significantly 0.6-4.1 GJ/yr.