Compact Simulation Model of Non-air Conditioned Room and Estimation of Its Thermal Characteristics under Winter Conditions.

Abstract

This study investigates thermal behavior of an occupied room exposed to winter weather conditions by means of quasi-steady-state model of the room. The space is not air-conditioned during the winter season, i.e. there is no humidity control and thermal performance of heaters maintains desired indoor air temperature. To obtain pure thermodynamic characteristics of the space, the model was set up and a series of tests was carried out in order to validate the mathematical model and find the thermal characteristics of the enclosure, which could be used directly for direct control techniques (DDC) if applied. The build -up model's method imposes boundary conditions onto room-faced surroundings walls and couples Fourier equations' thermal network employing modified Biot number. It also enables us to simulate an hourly energy use as well as heat flux calculus based on sub-hourly time steps. The model features a water equivalent content of the room, time-varying heat transfer coefficients, and boundary conditions onto surrounding walls, respectively. As a full dynamic method it accounts for thermal influence of outdoor climate conditions, occupancy use and other internal sources of thermal energy. The paper emphasizes selection of system boundaries and practical calculus of radiation heat exchanges without claiming shape factor algebra. The numerical results of temperature transient time responses obtained from mathematical model are well in accordance with those obtained from measurement in the actual room.