冷板内共晶溶液冻结过程数值模拟

冷板充冷时,共晶溶液降温、冻结过程中温度场不均匀,从而延长了其总体冻结时间.用焓法建立了蒸发盘管外共晶溶液冻结过程的二维导热数学模型,在二维柱面坐标下用控制容积法对导热控制方程进行离散化处理,并对共晶溶液的降温、冻结过程进行数值计算,指出可以通过调整蒸发盘管的布置方式,使冷板内共晶溶液温度场尽可能均匀、完成冻结的时间接近,从而缩短充冷时间,达到节能的目的.     

冷板冷藏车内冷冻板冻结过程数学模型的建立

目前冷板的充冷时间长,延长了货物运转周期.本文通过建立冷板冷藏车内冷冻板冻结过程数学模型,并采用C语言编程,计算了不同外气温度、太阳辐射、车厢漏冷、调温孔口等对冷板充冷时间的影响程度,为进一步研究冷板的充冷过程提供了理论参考.     

冷板冷藏车放冷时间影响因素探讨

本文根据热平衡原理对冷板放冷时间进行了分析计算,讨论了共晶溶液融解潜热、质量、以及环境温度、太阳辐射、车门漏冷、车体蓄冷、货物呼吸热和共晶冰过冷等对冷板放冷时间的影响.研究表明:共晶冰融解潜热是影响冷板放冷时间的关键因素,并提出了延长冷板放冷时间的措施和办法,为今后冷板冷藏车的运用和冷板的设计提供了重要理论依据.     

蓄冷板冻结与释冷的实验研究

通过实验的方式,分别研究了初始温度为30℃的Na Cl蓄冷板在-25、-35和-40℃的环境中的冻结过程以及初温度为-25℃的Na Cl蓄冷板在-10、-5和0℃环境中的释冷过程。实验结果表明:在冻结过程中,当环境温度低于Na Cl共晶液的共晶温度-21.2℃时,环境温度对共晶液开始结晶的时间有较大影响,而对共晶液从开始结晶至完全冻结过程所需时间影响较小;释冷过程中,环境温度高于Na Cl共晶液共晶温度-21.2℃时,外界环境对蓄冷板释冷所需时间以及共晶冰开始融化到完全融化的过程影响较大。     

蓄冷板释冷过程的数值模拟和实验研究

对蓄冷板内共晶液的热力学特性进行了分析,并且建立了蓄冷板释冷的数学模型。通过数值模拟的方法,模拟了NaCl蓄冷板在初始温度为-30℃,环境温度为-10℃、0℃和10℃三种不同温度条件下的释冷过程,并且通过相关的实验研究,对模拟结果的准确性进行了验证。通过研究得到了蓄冷板在不同条件下的释冷过程及特点。研究结果表明:在NaCl蓄冷板的释冷过程中,当其所处的环境温度高于-21.2℃,即其共晶温度时,外界环境温度会对冷板内共晶冰开始发生相变的时刻产生较大影响;外界环境温度越高,蓄冷板内共晶冰开始融化到完全融化所需要的时间越短。计算结果与实验结果吻合良好,两者之间的平均偏差小于0.5℃,说明数学模型及计算方法的可靠性。     

冷板冷藏车内冷板换热性能的研究

采用焓法的处理方法对冷板冷藏车内冷板的相变传热问题进行研究。通过数值模拟计算得到冷板的最佳厚度及管间距;保证当冷板外表面过热到-5℃时冷板内共晶冰全部融解,同时又能保证冷板尽可能蓄更多的冷量,为冷板车内冷板结构设计提供参考。     

冷板内共晶冰融解过程数值计算

机械冷板冷藏车冷板的放冷是保证货物质量的一个关键,而放冷过程受到多种因素的影响,从而造成冷板放冷不均匀的现象。本文建立了冷板放冷的数学模型,采用显热容法对冷板放冷的过程进行了分析；指出了冷板内共晶溶液的传热性能不佳是影响冷板放冷不充分的主要因素,并探讨了解决冷板放冷过程中出现的放冷不均匀现象的方案。     

机械冷板冷藏车冷板放冷数值模拟

机械冷板冷藏车冷板的放冷是保证货物质量的一个关键，而放冷过程受到多种因素的影响，从而造成冷板放冷不均匀的现象。本文建立了冷板放冷的数学模型，采用显热容法对冷板放冷的过程进行了分析。指出冷板内共晶溶液的传热性能不佳，是影响冷板放冷不充分的主要因素，并探讨了解决冷板放冷过程中出现的放冷不均匀现象的方案。     

普朗克食品冻结时间计算式与蓄冰时间的计算

按照普朗克食品冻结时间计算式的推导前提与思路，推导了在对流换热边界条件下，初温为0℃朱在盘管外在蓄冰球内蓄冰时蓄冰时间的计算式，并提出了计算蓄冰用水初温高于0℃时蓄冰时间的修正系数。     

外融冰盘管蓄冷动态特性研究

本文分析了外融冰盘管的工作过程，并对其蓄冷过程建立了数学模型，利用该模型模拟了冰盘管的蓄冰过程，其结果与实测值相近。该模型可为冰盘管蓄冰系统的设计提供理论根据。     

机械冷板冷藏车冷板融冰过程数值计算

用焓法模型建立了冷板融冰过程的数学模型，采用控制容积法对方程进行离散化，并用三对角矩阵算法求解出各节点的焓值和温度，分析了冷板厚度和车内空气温度对冷板融冰过程的影响；结果表明，冷板中心融解缓慢，冷板厚度对融冰过程影响比车内空气的影响大，减少冷板厚度将大大减少融冰时间。     

低共熔冰过冷问题的研究

本文通过分析低共熔冰过冷机理 ,得出结论 :过冷是为结晶过程提供推动力 ,在纯净、无杂质液态物质冻结所必须的 ;成核剂的存在 ,可以大大减小过冷度。经过过冷度测定实验和熔化潜热测定实验发现 :对于机械冷板冷藏车的冷冻板用共晶液 ( KCl溶液 ) ,Cu S是最合适的成核添加剂 ,在一般场合下也可以考虑使用 Si O2 作为成核剂     

Crystal ice formation of solution and its removal phenomena on inclined cooled plate

Experimental studies for freezing phenomena of ethylene glycol solution on an inclined polyvinyl-chloride plate have been performed. It is found that the crystal ice formed on the inclined cooled plate is removed from the plate surface due to a buoyancy force acting on the crystal ice. It is shown that the crystal ice grows in a shape of sheet by joining with neighboring ice and that the ice slides along the inclined surface when it is removed. The onset of the ice removal condition is related to the cooling heat flux at the surface. The ice removal occurs more easily for the plate of large inclination than that of a small one.     

新型流态冰蒸发制冷循环及制冰量性能分析

介绍了蒸发过冷水制冰原理及系统流程,分析了相应的蒸发制冷循环,对单位质量(1k)干空气制冰量性能及影响因素进行了研究并建立了相关数学模型,计算结果显示,水的初始温度越高单位质量干空气制冰量越低,而单位质量干空气制冰量相同时水温越高对应的蒸发水量则越大,同时随着空气出口相对湿度增大,单位质量干空气制冰量也随之增加.另外,...     

Ice formation of aqueous solution and its removal phenomena around vertical cooled cylinder

Experimental and analytical studies for freezing phenomena of ethylene glycol solution around a vertical cooled polyvinyl-chloride cylinder have been performed. It is found that the crystal ice formed around the vertical cylinder is removed from the cylinder surface due to a buoyancy force acting on the crystal ice. The crystal ice slides along the cylinder surface due to buoyancy force and grows in the shape of a tube by joining with the neighboring ice. It is shown that the onset of ice removal condition is related to the heat flux ratio, ‘from the cylinder surface into the cylinder’ to ‘from the cylinder surface into the solution’. The ice removal occurs more easily for short cylinders than for long ones.     

The Lyophilization of Dispersed Systems: Influence of Freezing Process,Freezing time,Freezing Temperature and RBCs Concentration on RBCs Hemolysis

ABSTRACT

In this work, we studied the influence of different parameters controlling cooling stage on biological dispersed system injury. The human red blood cell (RBCs) was chosen as work model. The study examined the influence of two freezing processes on RBCs hemolysis, one process producing big crystals, the other producing small crystals. Using both processes, we examined the effect of freezing temperature, freezing time, and RBCs concentration on injuries to RBCs. Freezing damage was assessed by the hematocrite measure before freezing and after thawing. The process producing a small number of big ice crystals (Pa) seems—in relation to the one producing a large number of small ice crystals (Pb)—to be less traumatic for the RBC, although the two are not statistically different. Freezing temperature and freezing time influence the preservation of RBCs. At 0 and ?20°C there were high preservation and total hemolysis, respectively. At ?5°C and ?10°C, the RBC hemolysis depends on freezing temperature and freezing time. The RBCs hemolysis rates increases when freezing time increases and when freezing temperature decreases. The rates of RBCs preserved decreases with RBCs concentration some with either the freezing process used (Pa or Pb). More, an accentuation of the difference between the two used freezing processes on RBCs hemolysis was retrieved. The analysis of the conductivity evolution within the RBCs suspension frozen showed that the destruction of the RBCs is had essentially to the solution effects. When the crystallization eutectic takes place, the RBCs are already completely destroyed.