The calculation of building cooling under emergency conditions to ensure their heating reliability

Abstract

Introduction. Continuation of research in the area of premise cooling rate calculation with the aim of obtaining dependencies, which are sufficiently accurate and take into account the most of the factors essential for the problem, but at the same time having an engineering form, is still relevant. The purpose of the study is the search for a dependence of the temperature in the building premises on time in the initial period after heat supply shutdown at emergency mode. Exponential nature of this dependence is considered as a scientific hypothesis. Materials and methods. The basic equations connecting the most important components of a heat flow in a cooling room under condition of the termination of heat supply from heating devices are used and analysed in the study. A numerical model of non-stationary thermal regime of the ventilated room is implemented on the base of the solution of a differential equations system of heat conduction and heat transfer on the surfaces of the room. Results. An analytical expression is obtained for the room cooling rate when the heat supply is disconnected, which has the form of an exponential function of square root of time since the accident. The cooling time before the condensation on the inner surface of the enclosure is determined by the example of a currently existing residential building under climatic conditions of Moscow, accounting the structural characteristics of the building and normalized fresh-air flow rate. Conclusions. It is shown that the building cooling in the initial period is influenced mainly by the ratio of the heat flux associated with unorganized air exchange and the heat loss to the environment through “light” enclosure. It was found that the decrease of natural air exchange in the building cooling process leads to a certain slowdown in the decrease of temperature, but it is not decisive. It is understood that the use of airtight light opening fillers, for example, in plastic casement, under normal conditions aggravating the sanitary and hygienic situation in the premises, under emergency conditions increases the available time interval for the restoration of heat supply.