Heating and cooling buildings by flow of water over the roof

Abstract

This paper presents an analysis for the reduction of the heat flux that occurs by constant flow water in a network of pipes buried in a roof. An air gap is introduced into the roof to achieve maximum thermal load levelling. A periodic solution of the one-dimensional partial differential equation (describing the temperature distribution in the roof) which also satisfies the appropriate boundary conditions, has been obtained in an explicit form. It is seen that, for a hot summer's day in New Delhi (the 26th of May. 1978), and for a water flow rate equal to 6 litres/h m 2, the heat flux entering the room is reduced, and that the collection efficiencies for a water heating system with glazed/blackened and bare top, surfaces are 49·0% and 8·27%, respectively. For a cold winter's day in New Delhi (the 9th of March, 1979), glazing and blackening the top surface of a room causes heating of water along with an enhancement of heat flux coming into the room. The time difference between the maxima of the heat flux entering the room and tha maxima of solair temperature is 8–10 h.