Heat Transfer 课程报告.docVIP

Course Report for Special English Department： Chemical Environment Engineering Title: Heat Transfer Class-mark： Name： Time： 2012-04-17 Heat Transfer 0908101-03 Tang Yining Abstract:The purpose of this paper is to present heat transfer information and the apparatus of radiation and convection are coupled.By varying heater temperature and air flow rate, we were able to verify that the apparatus works in accordance with theory by looking at the trends obtained by analyzing the results. As heater temperature increased, convection and radiation both increased. In addition, the percent of overall heat transfer that came from radiation increased as well. Keywords:heat transfer ;conduction;convection;radiation 1、Introduction Heat Flow. Heat is always being transferred in one way oranother，wherever there is any difference in temperature. Just as water will run downward，always flowing to the lowest possible level，so heat，if left to itself，is transferred from the hot to the cold objects，always warming the cold objects at the expense of the warmer ones. The rate at which heat flows depends on the amount of temperature difference as well as on the properties of the material through which it has to flow. There are three ways in which heat is transferred. Since heat itself is the energy of molecular activity，the simplest mode of transfer of heat，called conduction is the direct communication of molecular disturbance through a substance by means of the colllisions of neighboring molecular. Metals contain so-called free electrons, which make them good conductors of electricity ; these electrons also contribute to the conduction of heat，so metals have high thermal conductivities. Convection is the transfer of heat from one place to another by actual moti