双岛陈列柜融霜能耗及其节能的研究

以隆化集团德宝冷链有限公司双岛柜为例,从能耗分析方面阐述了超市双岛陈列柜冷冻冷藏融霜节能技术．在分析冷柜蒸发器的结霜融霜特性情况下,指出其在优化设计中的应用前景。     

智能热气融霜在低温并联制冷系统中的应用

通过对冷库内负荷以及冷风机结霜情况的分析,计算出在融霜时,需要投入的热气负载的量.同时采用热回收装置,把系统废热储存起来,在需要融霜的时候,利用蓄能提供热气负载,从而实现真正意义上的按需融霜,解决了低温并联系统热气融霜过程中热气量不足这一难题.     

石墨烯电热涂层在热泵机组抑霜/除霜上的应用研究

文中通过对室外换热器翅片冬季除霜的问题进行技术研究分析,在总结前人研究经验的基础上,改变换热器翅片的表面特性,利用环氧树脂石墨烯的疏水性能,并结合电加热的除霜技术制备出一种新型疏水性电加热涂层换热器。经测量证实了该涂层具有疏水性,在不同的电压及温度下对该涂层进行测试,发现不同含量的石墨烯对涂层的温升速率及温度稳定值呈正相关,并且该电加热涂层在低温工况下,电阻能够保持稳定,性能良好。另外,还在此基础上对该复合涂层的结霜融霜过程进行模拟,发现提高石墨烯含量可以抑制翅片的结霜速率,抑霜效果增强,通过与传统的电加热融霜方式模拟发现,复合涂层的融霜效果更加优越。     

冷媒除霜系统应用于冻结库时除霜性能研究

基于优化冷风机结构为目的的冷媒除霜系统应用于冻结库中,通过采用6mm翅片间距的冷风机进行冻结过程中除霜与不除霜的对比实验。并且研究除霜过程对库温波动、冻结物温度波动、冻结时间等参数的影响,以及系统运行的特性。研究表明:应用冷媒除霜系统,每次除霜对库内造成的温度波动都在5℃以内、除霜过程对冻结物温度不产生波动、除霜情况的冻结时间较不除霜缩短了一小时,并且选择除霜对系统更节能。因此,在冷媒除霜系统中采用适时除霜的方式不仅可以避免翅片间隙被冰霜封堵,还可以缩小冷风机翅片间距。在相同换热面积下,缩小冷风机翅片间距还可以达到减小冷风机体积和占地面积的效果。     

霜增长对隔栅片管式热交换器性能的影响

霜增长对装有隔栅片的热交换器性能影响的实验研究业已完成。霜的累积、横贯热交换器的压力差和基于对数平均热函差(LMED)的能量转换系数,在作为空气湿度、空气面速度和叶片间距函数的结霜条件下被定量化。较高的空气湿度、空气面速度和较小的叶片间距都会导致结霜增长的加快、较高的压力差和较高的能量转换系数。因为热交换器上霜的堆积,总能量转换系数最终就会下降。这些趋势始终与这篇文献所报告的保持一致。     

阻霜型空气源热泵多用机中央空调的应用

本文论述了阻霜型空气源热泵中央空调热水两用机组,由单制热改进为制冷制热一机二用,解决了冬天极端气温下制热的融霜问题。在-30℃正常使用,化霜时产生的余热全部回收,装机功率比分体式空调可减少40%,而且在冬季化霜时升温快、能耗低。空气源热泵中央空调配套热水器系统与分体式空调配套聚热式电热水器系统相比,在非极端天气下,可节能约66%。在极端天气下,可节能50%。     

铝表面结霜现象的实验研究

实验研究了自然对流时水平铝表面上的结霜现象.实验中空气温度25 ℃、湿度50%,冷面温度-40～0 ℃.与先前的铜表面实验结果类似,在冷面温度高于-38 ℃时,结霜前铝面上首先出现水珠;冷面温度越低,过冷水珠存续的时间越短,冻结温度也越低;冷面温度较高时,水珠冻结时引起的壁温回升较明显;不同冷面温度对应的初始霜晶形状不同;结霜过程中霜层表面新形成的霜晶形状随时间变化.将冷面温度降至-38 ℃后再与湿空气接触时,发现直接出现霜晶而未经过结露阶段.     

低温冷冻展示柜的电加热融霜节能分析

超市在人们生活中地位越来越重要,冷冻冷藏展示柜作为超市必备的一种制冷工具,当前正迎来快速发展时期。同时冷冻冷藏展示柜属于高耗能设备,耗电量占整个超市耗电量的30%以上,融霜作为展示柜耗电的重要环节,减少其耗电量对超市节能减排、降低运行成本具有重要意义。     

蒸发器除霜起点确定的理论与实验研究

通过建立压缩机能耗数学模型，编写VB程序进行模拟，最后加以实验验证得出利用压缩机能耗分析法进行冷库除霜控制可以达到库温波动小，压缩机能耗较小，节省能源的目的。     

电热装置的节能及其标准化

在概述电热装置的基本能耗状况后,总结了电热装置的八大节能途径及其相应措施,讨论了某些节能措施可能的负面作用和安全问题以及电热装置节能的标准化工作,并提出了一些建议.     

Comparison between hot-gas bypass defrosting and reverse-cycle defrosting methods on an air-to-water heat pump

Frost build-up blocks the gap between fins and decreases the airflow rate, and the heating capacity and COP of air-source heat pump become lower. The reverse-cycle defrosting (RCD) and hot-gas bypass defrosting HGBD are the two common methods of frost removal. The comparison between the RCD and HGBD methods on one heat pump were not found by authors up to now. This paper compared the dynamic characteristics during the RCD and HGBD periods on one medium air-to-water heat pump of 55 kW. The feasibility of the HGBD method without heat provided to evaporate the liquid refrigerant after melting frost, which was supposed in the danger of the compressor liquid slugging, was especially discussed. The results showed the liquid refrigerant leaving the air cooled coils for the HGBD method was trapped in the suction accumulator and flashed into the saturated gas by the compressor pumping action, and no compressor liquid slugging happened in our tests. The HGBD time was much longer than the RCD time. The amenity for the HGBD method was better than that for the RCD method, due to lower refrigerant noise, smaller indoor temperature fluctuation, and no cold blowing. The suction superheat and discharge superheat for the HGBD method were lower than those for the RCD method. The HGBD could overcome the main disadvantages of the RCD method and deserved the further investigation.     

Efficient defrosting of an inclined flat surface

We present a deicing simulation for a practical three-dimensional geometry inside which hot air jets impinge upon a flat inclined glass surface with a layer of ice on the outside. The main goal is to study the unsteady two-phase melting process over the inclined flat surface, and to identify the traditional control parameters such as jet impingement angles for minimization of the defrosting time for given ice and glass thicknesses. A correlation for defrosting as functions of time, heat transfer parameters and impingement angles has been found. Also, in this study, the first Joule heating defroster using transparent electrodes are proposed and numerically simulated as a viable alternative. A correlation between the electrical Joule power requirement and the defrosting time is given. It is demonstrated that substantial improvements (roughly 70% reduction) in defrosting time may be achieved using Joule heating compared to the traditional jet impingement HVAC technology.     

多联机不停机除霜的蓄热模块设计及实验研究

多联机热泵空调除霜技术一直是行业内的研究热点。通过仿真模拟对比了螺旋结构和平铺矩阵结构的蓄热模块对制冷剂管路放热的情况,选用了综合性能更优的平铺矩阵结构的蓄热模块与一台10HP多联机热泵空调器进行除霜匹配初步试验,结果表明,该独立蓄热模块不需要消耗热泵本身循环的热量,除霜期间完全不影响室内换热器的供热需求,除霜时间短,两次除霜间隔时间内,蓄热模块能顺利蓄热,实现了真正不停机除霜。     

Energy demand and comparison of current defrosting technologies of frozen raw materials in defrosting tunnels

The optimization process of coal defrosting in defrosting tunnels is solved in this article. Individual technical solutions of defrosting tunnels, as well as energy demands, are dealt with in this report. Defrosting tunnels are used for the defrosting of deep-frozen substrates like coal, ore or powdery substances. There are two different ways of defrosting. The first one is based on convective heating and the second one on radiant heating. Nowadays, convective heating is used much more than radiant heating. However, theory and practice show that the radiant heating is much more efficient. The aim of this article is to describe the design and construction of a multifunctional method of a defrosting tunnel. In the second stage we make experimental measurements of convective and radiant methods of defrosting on a built model. Its third aim is to make energy and economy assessments of defrosting process on the model. Finally, to implement the acquired knowledge in the practice, determining the conditions, in which the change of present-day convective defrosting technology to the new radiant technology becomes effective.     

热泵除霜特性分析

一、前言带热泵功能的空调越来越多 ,而且热泵运行时多采用热气除霜 ,作者至今未查到国内对除霜特性研究的文献 ,国外也多是实验研究。本文力图对除霜过程物理机理方面作些解释 ,根据实验数据指出减少除霜时间的措施及将除霜时用毛细管和用膨胀阀进行了对比。二、特性的实验研究除霜一般分为四个阶段 :除霜启动、融霜、排霜、除霜终止并恢复。系统图如图 1。制热时用毛细管节流 ,除霜时用热力膨胀阀。其中ＳＨＳＣ - 2 4 ,ＳＨＳＣ -2 5 ,ＳＨＳＣ - 2 6 ,ＳＨＳＣ - 17分别表示该点的过热度或过冷度。具体是用该点的温度传感器所测得的温度…     

风冷热泵机组中的热气除霜方法

针对风冷热泵机组在制热工况下容易结霜的特性 ,论述了利用压缩机排出的热气来除霜的方法 ,阐述了热气除霜循环的原理和过程 ,并提出了除霜总负荷及除霜时间的计算方法。其中除霜总负荷包括预热负荷和除霜负荷     

Defrosting method adopting dual hot gas bypass for an air-to-air heat pump

A novel dual hot gas bypass defrosting (DHBD) method is developed to remove frost from the outside heat exchanger (HEX) of an air-to-air heat pump. The proposed method adopts two bypass lines of hot gas from the compressor: one is connected to the inlet of the outdoor HEX, and the other is connected to the outlet of the exchanger. We compare the dynamic performance and defrosting time of the conventional reverse cycle defrosting (RCD), hot gas bypass cycle defrosting (HGBD), and DHBD methods using a medium air-to-air 16 kW heat pump. The salient feature of the DHBD method is its ability to prevent a sharp decrease in the compressor outlet temperature at the melting frost stage after the HGBD process begins. Due to the additional bypass, the DHBD method sustained a higher compressor outlet pressure and reduced the defrosting time by 36% compared to the HGBD method. Compared to RCD, the defrosting time was comparable (126%); however, the amenity characteristics of the DHBD method were superior than those of the RCD method. The proposed DHBD method can overcome the main disadvantages of the RCD and HGBD methods, and showed excellent performance for an air-to-air heat pump in a defrosting operation.     

空气源热泵除霜研究新进展

传统空气源热泵除霜方式不能满足室内温度及人体热舒适度要求。对不同除霜模式进行总结,从除霜工况对空气源热泵机组运行效率影响的角度进行分析,介绍热泵机组的研究现状,提出了一些不足以及相关的改进方法,为今后进一步除霜问题的研究提供了参考依据。     

Energy analysis and optimization of a food defrosting system

This paper illustrates the benefits of two energy optimization strategies to improve the overall process efficiency of a food defrosting system. First, an off-line energy analysis, including both the effects of the refrigeration cycle and the fan used to control the cooling air temperature and speed, is carried-out. This first approach puts on display an optimal running point of the process for a specific cooling air temperature value, which leads to an optimization of the overall energy consumption. Second, an on-line energy optimization approach, based on a nonlinear model-based predictive control strategy, is developed. This second approach takes simultaneously into account the expected thawing time, the highest temperature accepted and above all an energetic cost. Simulation results show the benefits of this on-line energy optimization to significantly increase the overall process efficiency. Indeed, this strategy leads to an optimization of the overall energy consumption whatever the expected thawing time and the inlet air temperature.