间接制冷系统中除霜、能耗及温室效应的比较

本文主要介绍间接制冷系统的流程原理,阐述了三种不同的除霜方式:暖液除霜、电加热除霜及热气除霜,并对在间接制冷系统中普遍应用的暖液除霜和电加热除霜进行了比较分析,结果表明暖液除霜更为高效.最后比较了直接制冷系统与间接制冷系统的能耗和温室效应影响,发现间接制冷系统的能耗更小,温室效应影响更低,对节能和环保有利.     

CO2制冷系统融霜方法的分析

本文结合CO2制冷系统的特殊性,通过对水融霜、自然融霜、电热融霜以及热气-水融霜几种不同的融霜方法进行对比,最终提出了利用热乙二醇为CO2制冷系统融霜,并对热乙二醇融霜方法进行了理论分析。     

户用空气源热泵机组除霜方法的实验研究

试验对比一台户用整体式空气源热泵机组的3种除霜方案：旁通制冷膨胀阀、风机提前启动和热气旁通融霜。结果表明,用外径16 mm的铜管旁通制冷膨胀阀是比较适合测试样机的除霜方法,在-3℃/90%工况下除霜时间由205 s缩短至99 s;当除霜温度设定为0℃时,提前启动风机可以避免系统的高低压出现大幅度的波动;而热气旁通融霜会导致机组的制热能力下降,但有利于机组在低温工况下的运行稳定性。最后对试验需要改进的地方进行简要说明。     

工业制冷中热氨融霜的优化配置

对工业制冷自动热氨融霜控制进行分析,从控制部件的角度确定影响热氨融霜的因素.根据安全、效率和节能的要求,对自动热氨融霜的控制系统提出优化配置方案.对优化前后的配置方案进行对比发现,通过合理的优化,工业制冷中的自动热氨融霜可以进一步获得更高的安全性、更好的融霜效率以及更低的能耗.     

Optimisation des dégivrages par gaz chauds en chambre à basse température

An investigation into energy expenses related to frosting and defrosting is very useful as it reveals all the technological strategies for minimizing energy expenses. In the case of cooling coils for ambient conditioning at very low temperature, certain solutions need to be changed when other expenses are involved or when they do not satisfy industrial safety standards. Nevertheless, hot gas defrosting gives significant advantages with the use of a heat pump. If ρ is the coefficient of performance of the refrigerating plant, all the expenses linked to hot gas defrosting benefit from the minor coefficient . All the terms of the general expression of the expenses are considered in this case and take on a particular relative importance. It is sometimes possible and more efficient to ‘fight’ the causes rather than to seek elaborate remedies. Management and automation systems are one way to solve this problem, and the different sensors able to control both the extent of frosting and the entire defrosting process are considered in this paper. Differential thermometers and manometers are most often used for frosting control; the ice capsule is a very efficient means of controlling the final steps of defrosting. It is certain that technologies are sufficiently developed to be used on an industrial scale; the common applications are only under development, and their practical advantages remain to be estimated even if their reliability and theoretical advantages are proven. For large cold rooms, frost entrapment is the solution proposed; it is more interesting from the point of view of air quality than from energy savings.     

冷库氟里昂制冷系统冷风机除霜模式的探讨

文章主要介绍冷库氟里昂制冷系统中冷风机的几种常见的除霜模式,深入分析、比较不同除霜模式的能耗,提倡氟里昂制冷系统的节能投入。     

多组并联蒸发器制冷系统的热气冲霜装置

介绍了当前制冷系统中除霜的研究现状和热气冲霜的原理,讨论了几个除霜的技术参数,提出了一种新型的多组并联蒸发器制冷系统的热气冲霜装置,并介绍了本装置的设计原理及工作过程。本装置采用多组别并联蒸发器分组化霜形式,部分组别蒸发器制冷,部分组别蒸发器化霜,相互之间温度影响很小,有利于食品的保存,当再次制冷时冷藏室降温快,压缩机功耗小,节能效果明显。     

液体冷媒融霜制冷系统融霜过程制冷温度变化规律的实验研究

液体冷媒融霜是一种新型的融霜方法。介绍了液体冷媒融霜实验装置,研究了在不同负荷不同库温下的融霜过程,从库温、融霜时间、制冷系统运行状态等方面分析了液体冷媒除霜系统对冷库的影响。实验结果表明:冷媒融霜可通过高压液体制冷剂与冰霜的热交换过程得到过冷来回收冰霜冷量。在被融霜蒸发器停止融霜后切换的瞬间,库温有较大幅度的上升。无负荷实验库温高于-5℃时,融霜过程库温依旧降低,说明液体冷媒方案可以用于制冷过程不能停止的速冻装置上。     

冷库液体冷媒融霜的性能实验研究

介绍了冷库液体冷媒融霜实验装置,对实验结果进行分析研究.与热气融霜相比较,液体冷媒融霜系统具有制冷量大,对换热器翅片效率影响小,室温波动小等优点,是一种可行的融霜方法.     

低温冷风机热气融霜实验研究

简述了低温冷库冷风机的热气融霜方式,对一座低温实验冷库进行了热气融霜实验.研究了在不同库温情况下的融霜过程,从库温、凝水量、温度场变化以及制冷系统运行状况等方面,分析了热气融霜对低温冷库的影响.实验结果表明热气融霜具有时间短、对库温影响较小等优点.     

超市陈列柜制冷系统热气融霜方案的探讨

主要探讨了超市陈列柜制冷系统热气融霜的两种方案;定性地分析了热气融霜的节能特性。     

用TRIZ理论解决微通道换热器除霜排水问题

近年来,微通道换热器（MCHE）受到制冷空调行业较高的关注。针对微通道换热器热泵应用时,化霜水比较难以排出这一微通道换热器应用的难点,笔者利用TRIZ理论分析MCHE除霜排水时的技术矛盾,提出多种解决方案。     

制冷剂流量控制法在风冷热泵除霜中的应用

根据热泵空调系统中制冷工况和制热工况时制冷剂流量的差别,采用制冷剂流量控制法对热泵空调系统中的制冷剂流量进行控制,并将制冷剂流量控制法与热气旁通法除霜相结合应用于热泵除霜过程中。结果表明,在控制制冷剂流量的热泵空调系统中,系统正常运行时,该循环系统能抑制或减缓室外换热器表面的结霜;当室外换热器表面结霜时,则可加速除霜,缩短除霜时间。     

某热气融霜管路供液过滤器爆裂事故分析的试验研究

介绍了一种新型的利用制冷系统中的压缩机高温排气对商用冷冻冷藏设备进行除霜的热气融霜系统。同时针对某热气融霜工程供液过滤器爆裂事故进行了分析和试验研究,试验数据重复性良好,进一步验证了系统的可靠性;研究结果还表明：热气融霜系统中大量阀件的正确安装顺序对于整个系统的安全、高效运行具有至关重要的作用。     

热气融霜自控系统及经济性分析

介绍工业制冷中霜层存在对节能的不利影响,对各种除霜方式进行分析比较。针对较为节能的自动热气融霜方式提出相应的解决方案,并分析该方案在安全和效率方面的具体控制策略。指出热气融霜自控系统具有节约人力成本和节能环保的优点。     

空气冷却器融霜方式的改进措施

分析了冷库中空气冷却器的结霜原因以及霜的特性，并尝试了几种新的融霜方式，以作设计借鉴。     

Mathematical modelling of thermal storage systems for the food industryModélisation mathématique de systèmes d'accumulation thermique utilisés par l'industrie alimentaire

Dynamic mathematical models of two thermal storage systems used in the food industry to produce chilled water are presented; an ice-bank system and a holding tank system. The variability of the refrigeration demand with time was taken into account in the model. A zoned approach using mass and energy balances was applied. Heat transfer phenomena in the evaporator were modelled using empirical correlations. The experimental validation of the mathematical models on an ice-bank system at pilot plant scale, and a centralized refrigeration system with a holding tank in a winery, showed accurate prediction. Simple models are adequate to predict the dynamic behaviour of these refrigeration systems under variable heat loads.     

Simulation of the transient response of heat driven refrigerators with continuous temperature control Simulation de la réponse transitoire des réfrigérateurs utilisant une source de chaleur avec maîtrise de la température en continu

A theoretical and experimental study is presented and a mathematical model is introduced for a heat driven refrigeration system operating with continuous temperature control. The model consists of a refrigerated space, an absorption refrigerator, operating irreversibly, a temperature sensor and a reference signal, and a power law control action. The steady-state behavior of the absorption refrigerator model is validated by direct comparison between theoretical results and experimental data. The model is then used to identify an optimal thermal conductance allocation, for a fixed total thermal conductance inventory, such that the refrigeration rate is maximized and the ‘pull-down' time is minimized. A simulation of the system operating in a transient mode is carried out to show that closed-loop operation results in a large reduction of fuel consumption, with respect to the ‘on–off' operation. Appropriate dimensionless groups are identified and the generalized results reported in charts using dimensionless variables.     

Le froid, élément de la sécurité alimentaire dans le monde

Improving food security is now a basic and one of the most difficult problems of world food policy and economy. The problem exists because of the need for faster growth in food resources than population levels, especially in the developing countries where food consumption per capita is very low. If refrigeration processes can be constantly adjusted in form to meet the needs of food economy, they can play an important role in the following areas: food reserves; reducing losses in food production and turn-over; reducing seasonal variations; international food trade development; increasing the possibilities for the world fish economy; and frozen food production. The building up of foof resources and consequent stabilizing of the world's food situation became possible mainly through the existence of cold stores. The total volume of all multi- and one-branch cold stores can be estimated as ap; 1.5 × 10⁸ m³. The USA, Japan, USSR, Canada, UK, France and FRG are among the major shareholders of this global potential. This volume could provide storage for 4 × 10⁷ tons of food requiring refrigeration. This is the equivalent to 10 days food production in the world. Further development of cold storage is, therefore, necessary. Although the exact estimation of losses from food production and turn-over is very difficult, many experts evaluate these losses as 20–30%. Some of these experts estimate tthat wide-spread use of refrigeration could save 2.5 × 10⁸ tons of food from deterioration per year. This is equivalent to 80 kg for each person in the world. A decrease in seasonal variation in food production is necessary to adapt seasonal food production to constant consumption. Cold storage can allow a gap of several months between food production and its consumption. Refrigeration has enabled the development of large-scale international and intercontinental food trade. At present > 3 × 10⁷ tons of food per year is involved in world trade (i.e. meat, butter, bananas). After World War 2 the total weight of fish caught increased very quickly from 1.9 × 10⁷ tons in 1948 to 7.2 × 10⁷ tons in 1980. This was possible only because of the application of refrigeration, especially at sea in large oceans. Frozen food production is seen by some as the biggest achievement of the twentieth century in food technology. Production of frozen food has been estimated as ap; 3.0 × 10⁷ tons per year, exclusive of the 1.0 × 10⁷ tons of ice-cream. Increased world food security depends on refrigeration techniques developing at a faster rate than population growth, as well as the growth rate of world food production.     

In-situ study of frosting and defrosting processes in tube-fin evaporators of household refrigerating appliances

The present paper advances an in-situ study of frosting and defrosting processes in tube-fin evaporators of household refrigerators and freezers. Frost growth experiments were carried out using a purpose-built test facility comprised of a refrigerated cabinet placed inside a climatized chamber, and a vapor compression refrigeration loop that controls both the evaporating temperature and the evaporator superheating. A first-principles two-dimensional simulation model was put forward to predict the evaporator blocking over time, and also the heat and mass transfer rates. The model validation exercise has shown that the model follows well the experimental trends of pressure drop, frost mass, cooling capacity and air flow rate, with all predictions falling inside ±10% error bounds. The model was then used to assess the impact of several design parameters on both the evaporator blockage and defrost efficiency. It was found that a nearly ideal defrost efficiency is achieved when the defrosting process is performed by two simultaneous heaters.