Experimental Study of Passive Cooling of a Building Using Long-Wave Night Sky Radiation in Owerri, Nigeria KY RADIATION IN OWERRI, NIGERIA

ABSTRACT

An experimental study of the passive cooling of a building using longwave night sky radiation in Owerri, Nigeria is presented. The experimental rig consists of a standard (3.0 x 3.0 x 2.5m) room, flat plate sky radiator, heat exchanger, storage tank, water pump, interconnecting pipes and another standard room to act as control for the experiment. This test rig is a rectangular building made from 15.24cm hollow blocks. It has two windows located in the east and the south facing walls respectively and an access door located directly opposite the south facing window. The roof is pitched at 12o to maximize the cooling potential of the building. Cold water from the radiator enters the heat exchanger through the inlet channel and fills its rectangular chamber. Heat from the room is transferred to the heat exchanger through convective heat exchange between the indoor air and the heat exchanger. This is made possible by the fact that cold air from the surface of the heat exchanger displaces the warm air in the room. During the daytime, the

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cooled water stored in the storage tank is circulated between the heat exchanger and the storage tank, while the radiator is isolated with the aid of a control valve. Series of tests were conducted under the meteorological condition of the Federal University Of Technology, Owerri, Nigeria for the period spanning 13March 2010 to 30 November, 2010 and in April 2011. The periods are within the major climatic seasons of Nigeria. The results obtained showed that minimum water temperatures ranging over 21oC – 230C were obtained through night sky cooling in Owerri. During the day, the cooled water was passed through the heat exchanger to cool the space. The results obtained for the daytime cooling yielded a maximum temperature depression of 3.5oC below the recorded average room temperature of 28oC.This value translates to 1428kJ of useful cooling. The above results revealed a great promise for use of passive cooling technique in buildings in our tropical region. Application potentials for nocturnal cooling also exist for the storage of agricultural products like fruits, vegetable etc.