本章的学习目的 (1)分析实际传热问题的能力 (2)综合应用三种基本传热方式及其相关公式的能力 (3)了解换热器的基本知识和设计过程 §9-1 传热过程的分析和计算 §9-2 换热器的型式及平均温差 § 9-3 换热器的热计算 § 9-4 传热的强化和隔热保温技术

1、重点内容: ①非稳态导热的基本概念及特点; ②集总参数法的基本原理及应用; 3一维及二维非稳态导热问题。 2、掌握内容: ①确定瞬时温度场的方法; ②确定在一时间间隔内物体所传导热量的计算方法

1 热辐射特点 (1)定义:由热运动产生的,以电磁波形式传递的能量; (2)特点:a任何物体,只要温度高于0K,就会不 停地向周围空间发出热辐射;b可以在真空中传 播;c伴随能量形式的转变;d具有强烈的方向性 e辐射能与温度和波长均有关;f发射辐射取决于 温度的4次方

1、重点内容: ①掌握导热问题数值解法的基本思路; ②利用热平衡法和泰勒级数展开法建立节点的离散方程。 2、掌握内容:数值解法的实质。 3、了解内容:了解非稳态导热问题的两种差分格式及其稳定性

8-1角系数的定义、性质及计算 两个表面之间的辐射换热量与两个表面之间的相对位置有很大关系

What is Convective Heat Transfer? You have already experienced it. Difficulty lies in generalizing our experience; filtering it down to a few laws: learning how to apply these laws to systems we engineers design and use Here is what i want you to do:

Heat Exchangers, LMTD Method Where we’ ve been. So far have focused on detailed heat transfer analysis of specific conditions, such as external heat transfer coefficient Where were going: Investigate methods for larger system level analysis that combine all these modes of heat transfer in heat exchangers

Heat Exchangers. NTU-8 Method Where we’ ve been∴ Analysis of heat exchangers using log mean temperature difference (LMTD)

2-1基本概念 2-2一维稳态导热

Natural Convection Where we’ ve been Up to now, have considered basic concepts of natural convection, the governing equations and laminar free convection on vertical surface Where were going Consider empirical correlations for natural convection Heat Transfer