Research On The Heat Load And Indoor Thermal Environment In A Room With Low Temperature Heating

In recent years, with the rapid development of national economy, citizens pay more and more attentions on indoor thermal environment. Low-temperature heating technology becomes more and more popular and is widely used in the HVAC field because of its advantage of energy saving and thermal comfort. Low-temperature heating devices,especailly the radiant heating devices, the heat transfer characteristic is different from the room with the radiantor; thus the heat load and thermal comfort is different on condition that the indoor and outdoor temperature difference is equal. The steady and unsteady state simulation models are built with classical heat and mass transfer theory and the difference and the variation regularity of the heat load and thermal comfort in the room with Low-temperature heating and the room with radiantor is studied in this paper.Firstly, the paper analyzes thermal performance of the different energy-saving stage of building envelope in severe cold area and cold area. The parameters-heat transfer coefficient, outdoor temperature, the radiant panel temperature etc.are indentified through the literature material.Secondly, the physical model is built according to the common residential building in North China and the mathematical models of the room with radiant heating and convection heating are built with classical heat and mass transfer theory and validated by the experiment. The research tests the temperature in a room with radiator in a period of January, 2011 and February, 2011and analyzes the variation of temperature during the period.Thirdly, a simulation of the room with low-temperature heating is undertaken in sereve cold area and cold area and the steady-state temperatures and unsteady-state temperatures are obtained. The heat load of model room and its comparison with the room of radiator is given by theory analysis. The coefficient of heat load between the room with Low-temperature heating and the room with radiator is concluded through the comparison. The results of this paper show that the heat load in a room with low-temperature heating mentioned in this paper is different than the result in a room with the radiator. The coefficient of heat load between the room with Low-temperature heating and the room with radiator in severe cold area is from 0.90 to 1.08 . In cold area, the coefficient is from 0.86 to 1.105. The paper also summarizes the unsteady-state heat load and its variation regularity according to the simulation. Through the study, the variation regularity of indoor environment temperature and heat load in a room with low-temperature mentioned in this paper is very small.Finally, the indoor air temperature range meeting the thermal comfort and the variation regularity in rooms with different Low-temperature heatings is obtained with the steady-state temperatures and unsteady-state temperatures mentioned above. When the thermal resistance range of the staff clothing is from 0.8clo to 1.4clo, the comfortable air temperature range in a room with radiant heating is 16.88 ~ 24.24℃; and 17.29 ~ 24.75℃in a room with natural convection heating. the comfortable air temperature range in a room with forced convection heating is 0.6 ~ 0.8℃higher than the temperature in a room with natural convection heating because of the higher wind speed. This paper also suggest that the fluctuations of PMV index and indoor environment temperature in model room is very small regardless of energy stages and the low-temperature heatings in model room and the indoor environment is stable in model room mentioned in this paper.This paper can be a reference for the preparation and revision of industry standards in application of Low-temperature heating.