A cost saving air-condition system through earth cooled dehumidification

Abstract

The objective of this research is to design a cost saving air conditioning system which instead of using outdoor compressor unit to chill and dehumidify the air, is cooled and dehumidified by the earth. Conceptually, in this air-conditioning system, atmospheric air is sucked into the space or room to be conditioned through a filtered opening of a ducting network. The ducting network is entirely (except suction opening piece) installed at least 2m deep underground and is made of highly conductive metal so that it Can absorb most of the heat in the atmospheric air that being sucked into the room or space and transfer the heat to the surrounding earth in contact with the external surface of the ducting. The air passage in the underground ducting is designed in such a way that the air flow pattern provides the optimum conditions for the maximum heat transfer such as interface area and retention time. The cooled and dehumidified air from the buried ducting is then distributed evenly into the room or space from underneath the floor area through hundreds of evenly located hidden diffuser holes. The air will then rise up to the ceiling while conditioning the room and partially sucked out by a solar powered axial exhaust fan through the outlet. In ensuring the most efficient design of the system is achieved, the understanding of heat transfer and characteristic of air especially on humidity and temperature is inevitably necessary. As it is expected that this air-conditioning system could not cool down the air lower than the temperature of the earth or medium burying it, the study is focused on analyzing all possibilities of replacing the original soil with the soil that has the highest thermal diffusivity and the use of the sodium chloride solution in order to promote heat diffusivity. The method of research is by conducting lab-scaled experiment to determine the most suitable metal for the ducting with the best shape so that the optimum configuration for maximum cooling could be achieved. The most suitable type of earth or medium in contact with the underground ducting is also identified by conducting field test using long thermometer probe to analyze the temperature profile of various type of land in Malaysia. The testing of various types of earth and its combinations on their heat absorption and thermal diffusivity is also conducted in the KUTKM's laboratory using a special test rig. In the next scope of research, the shape of the dehumidifier's diffuser grill or fins shall be desimoisgn moisture condensation process shall completely take place before treated air is released into the room or space in order to condition the room to the required temperature and humidity. The condensate shall be collected into a sump located underneath the dehumidifier and at down stream of the ducting and is intermittently emptied by a small capacity pump powered by solar energy. The temperature of the room could be controlled via thermostat by sending an auto-feedback signal to regulate the speed of solar powered axial suction fan by means of frequency inverter or current adjuster in order to control the air flow-rate into the room. The ducting system is perfectly sealed in order to prevent insects and small organisms from entering and inhabiting the ducting network. The ducting size should be large enough for the maintenance person to enter up to the dehumidifier section.