Using heat pipes in greenhouse heating

Abstract

In the present work an instrumented heat pipe is designed, constructed and inserted inside a greenhouse to be used as a heating source during night or cloudy days in the cold months. Transferring geothermal heat from underground to the surrounding inside the greenhouse without consumption of conventional energy is one of the latest applications of the heat pipe device to transfer heat. The heat pipe is made of a sealed metal tube containing water as a working fluid. It is divided into three sections; the evaporator, adiabatic section and condenser. The buried part of the heat pipe is the evaporator section which transfers heat from the underground soil to the working fluid, which is in turn, transfers heat to the condenser where it is rejected to the surrounding inside the greenhouse. This study was conducted on a greenhouse with an area of (3.75)m2. Two heat pipes inserted at different depths inside the greenhouse soil were used to investigate the performance of this device. Results show an increase, with stability, of the environment temperature inside the greenhouse when the heat pipe is implemented in the cold and cloudy days of the cold winter months. The temperature inside the greenhouse reached (20)oC when the heat pipe inserted inside the soil to a level of(3.5)m with heat transfer rate of (126)W, while the outside temperature was about(14)oC.