Design Parameteres of an Earth-Air Heat Exchanger with a Square Cross Section - Case Study: Greenhouse

Among renewable and clean energies, geothermal energy is superior to other types of energy, and unlike other renewable energies, it is not limited to the season, time, and conditions. One of the applications of geothermal energy is the use of ground heat at shallow depths as the earth-air heat exchanger (EAHE), which is used as a modern and effective technique for preheating the air in the winter and vice versa precooling in the summer. In this study, the design of an EAHE converter for a commercial greenhouse for heating or cooling purposes was examined. A one-dimensional model of the EAHE system was developed to evaluate the effects of main parameters such as diameter, length, air flow rate, and fan power and system efficiency. Given the direct relationship between number of the transfer units (NTU) and the effictiveness of EAHE (ε), it is possible to construct an EAHE system in order to obtain an appropriate NTU and its ε and handle the design of an EAHE system to a point where these two parameters will be obtained with the desired values. By the model and method presented in this study, the effects of main parameters as the effective design factors can be simply assessed without any waste of energy and time and complexity.