下霜的

The thesis can be divided into five parts as follows: First, the structural characteristics of finned-pipe evaporator are analyzed. After selecting suitable microelement controller, the heat-transfer and mass-transfer processes are analyzed for every microelement under the conditions of dryness, wetness and frostiness. Based on previous equations, some parameters of frostiness are confirmed and the frost-growing model is set up under frost condition. Some hypotheses are postulated and with the help of the equation of mass-conservation, energy-conservation and momentum-conservation, the evaporation model which fits in the dynamic simulation is built, which set a solid foundation for system simulation. Second, the starting and stopping behaviors under disturbed condition are analyzed and calculated by using the dynamic concentrative parameter model, which gives some advice to better prescribe refrigeration system and set theoretic foundation for carrying out automatic control of refrigeration system. Third, the normal running process is analyzed and calculated by means of rational matching theory, which gives some advice on how to better understand the parameter change under steady state and the affection of inlet-parameter on evaporator. Fourth, the simulation software with dynamic characteristic is designed, which can be applied to calculate thernio-parameter of cryogen, air humidity and frost thickness under different initial and boundary conditions, and to carry out dynamic simulation under conditions of dryness, wetness and frostiness, at the same time, to achieve detection and simulation at any stage from starting to stopping.

本文的主要内容如下：1对翅片管蒸发器结构特点进行分析，选取适当的微元控制体，就干、湿和霜工况下对每个微元分别进行传热传质分析，基于经验关系式确定霜的有关参数，对于霜工况下的霜生长建立模型，经适当假设，运用质量守恒、能量守恒和动量守恒方程建立适合动态仿真的蒸发器数学模型，为系统仿真奠定基础； 2对蒸发在大扰动下的开、停机过程，运用动态集中参数模型进行分析和计算，为更好地描述制冷系统运行的全过程奠定基础，同时也为制冷系统实现自动控制提供一定的理论基础； 3对蒸发器正常运行过程，运用动态分布参数和参数间定量耦合的观点来分析和计算，为更好地了解稳态工况下各点参数的变化情况及各入口参数对蒸发器动态特性的影响即蒸发器性能对各参数变化的敏感性； 4编写翅片管蒸发器动态特性仿真计算程序，可以计算不同边界条件和初始条件下的制冷剂热力参数、空气温湿度和霜厚度分布场，实现对翅片管蒸发器在干、湿和霜工况下的动态仿真。

It looked as if the city might be in for a frosty spell.

看样子这座城市可能会有一段下霜的日子。

This is the way we wash our hands on a cold and frosty morning.

在一个寒冷，下霜的早晨，我们就是这样洗洗手。

This is the way we dry our hands on a cold and frosty morning.

在一个寒冷，下霜的早晨，我们就是这样弄干手。

This is the way we clap our hands on a cold and frosty morning.

在一个寒冷，下霜的早晨，我们就是这样拍拍手。

This is the way we jump about on a cold and frosty morning.

在一个寒冷，下霜的早晨，我们就是这样蹦蹦跳跳。

This is the way we comb our hair on a cold and frosty morning.

在一个寒冷，下霜的早晨，我们就是这样梳梳头。

And at the same time, the interval of defrosting is obtained, which provides the basis for the adoption of effective defrosting measure.

而且计算出了不同工况下融霜的时间间隔，为采取有效的除霜控制方法提供了依据。

Compared with other methods of defrosting,hot liquid defrosting has some advantages in constant temperature and humidity air-conditioning system.

恒温恒湿系统一般都在结霜的工况下工作，目前的除霜方式都存在一些弊端。

On the one hand, the frost layer increases the thermal resistance in the airside, on the other hand, as the frost continued to grow, it restricts the airflow in the evaporator and also insulates the cooler surface from the air.

由于霜层的形成和增长对低温条件下蒸发器的性能有很大影响，因此，对蒸发器结霜过程进行理论和实验研究是非常必要的。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了