Investigation of Transient Process of Heat Carrier Temperature of Water to Air Heat Exchanger

摘要

Fuel and energy consumption in Lithuanian households in 2010 comprised 33,3% of total fuel and energy final consumption [1]. About 44% of this energy is consumed for building heating [2]. Automation is one of the ways for saving heating energy and making comfortable indoor environment of buildings. Intermittent heating of buildings is mostly implemented by programmable heating controllers. These controllers regulate temperature of heat carrier, supply to heating system, according to set program and depending of outdoor temperature and sometimes depending of both outdoor and indoor temperatures [3,4]. Temperature of supply heat carrier is regulated by controlled mixing of supply and return heat carrier. This mixing is implemented by two-way, three-way or four-way valves [3,4]. Temperature of supply heat carrier depends not only on position of mixing valve, but also on return heat carrier temperature and its dynamics. Radiators and water to air heat exchangers are mostly used for heat transfer from heat carrier to premises [4,5]. Quite many papers are published which analyze static and dynamic characteristics of radiators [6,7]. When investigating water to air heat exchangers, control channel "temperature of inlet heat carrier - outlet air temperature" is emphasized [8], whereas when designing and adjusting heating controllers one has to know the dynamic parameters of heat carrier temperature, returning of heat exchanger. The purpose of this research is to estimate the form of transient process of water to air heat exchanger outlet heat carrier temperature and to develop the transfer function for heat carrier temperature control needs. The response of outlet heat carrier temperature to the instantaneous change of inlet heat carrier temperature was analyzed.