Performance Evaluation of Earth Air Tube Heat Exchanger during Winter Season for Ludhiana Climate

Abstract

Due to the enormous use of energy worldwide, there is a remarkable gap in demand and supply of energy has triggered the researchers to use geothermal, a sustainable and renewable form of energy in the form of an Earth Air Tube Heat Exchanger (EATHE). An EATHE can effectively work for HVAC of buildings or greenhouses. AnEATHE system was installed, in order to evaluate the performance during the winter season. The EATHE was designed with a 152 mm diameter PVC pipe of 5.8 meters length, buried at a depth of 2.76 meters. Fresh air was circulated with an air blower, following an open-loop system. The EATHE was run four times a day i.e., morning, noon, evening and night, at velocities of 2.70 m/s, 4.76 m/s, 6.25 m/s and 7.69 m/s for 30 minutes duration each under the open system. The variation in air flow rate was achieved with help of a dimmer to get the steady-state condition and optimum results. The temperature gain and coefficient of performance (COP) were evaluated at these velocities. Hence the validatedEATHE system can be used for HVAC of buildings at its optimum air flow rates for Morning, Afternoon, Evening and Night time.It was observedthat 2.70 m/s is optimum air velocity to get higher temperature difference and COP during morning and noon sessions. The optimum value of air velocity for the evening session is 6.25 m/s because it gives a higher temperature difference of 7°C than any other air velocities. The COP for the evening session is slightly higher achieved than the airflow rate of 6.25 m/s, at a flow rate of 4.76 m/s. During the nighttime, the total temperature change is 7°C with three different airflow rates i.e., 2.70 m/s, 6.25 m/s, 7.69 m/s. The optimum value of COP is 13.5, which is achieved at 2.70 m/s air velocity, so 2.70 m/s can be considered as the optimum airflow rate for the night session.