Dehumidification and humidification process of desiccant solution by air injection

Liquid desiccant dehumidification was proved to be an effective method to extract the moisture from air with a relatively less energy. An experimental study was carried out to evaluate the liquid desiccant system performance during dehumidification and humidification processes using an injected air through the liquid desiccant solution (calcium chloride). A different air mass flow rates though the desiccant solution was considered during the experimental work. The desiccant system was studied at different operating conditions like different temperatures, different humidity ratios and different solution levels. The effectiveness for both the dehumidification and humidification processes was calculated through this work. It was found that, the system effectiveness reached to 0.87 in the dehumidification and about 0.92 in the humidification process. Also; the experimental results showed a mass transfer coefficient of 28 kg s⁻¹ m² mm Hg at an air mass flow rate of 0.022 kg s⁻¹ in the dehumidification process. The cooling effect factor was also studied and analyzed during that work.     

在螺旋套管冷凝器内R417a凝结换热性能的实验研究

在空气源热泵热水器中,使用混合型制冷工质R417a,冷凝器采用螺旋套管换热器且套管环形空间内制冷剂与内管中的水逆流换热。对在不同工况下,环形通道内R417a的凝结换热特性进行实验研究和理论分析。实验的工况为:水的体积流量为0.60～1.00 m~3/h,水的流速为0.58～0.98 m/s,冷凝器进水温度为20.0～55.0℃。实验结果表明:环境温度为15.0℃,螺旋套管内R417a的凝结传热系数随冷凝饱和温度的升高而减小,局部凝结传热系数随干度的增大而增大。当冷凝器进水体积流量为0.60 m~3/h,饱和冷凝温度由40.0℃增加至60.0℃时,冷凝器制冷剂侧凝结传热系数从3 839.0减小至2 372.0 W/(m~2·K),约减少了38.1%。     

Experimental study of free convection heat transfer and condensation of vapor of humid air over an inclined cold tube

In this study condensation heat transfer on a cold inclined circular cylinder due to natural convection for various conditions is investigated experimentally. The cylinder is placed in an isolated test room to permit pure natural circulation of ambient air. Ambient temperature and humidity of the test room are controlled by a refrigeration cycle and humidifying. The ambient relative air humidity changed in the range of 30 to 50% and temperature from 25 to 35 °C. The ethylene‐glycol/water solution is used as a refrigerant to control and keep the temperature of the test section at a constant value. The cold surface temperature is varied from 2 to 6 °C. The condensation rate and heat flux are found to depend mainly on time, temperature difference between ambient air and cold surface, ambient relative humidity, and tube inclination. Results are plotted for various conditions with respect to time. The experimental results are used to propose a correlation to predict the condensate mass flow rate for free convection heat transfer. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21015     

Experimental studies of low-temperature drying by dehumidification. Part 1—Apparatus and theory

The feasibility of using a heat pump is considered as an alternative to other forms of drying where low temperature drying of a substance is necessary, either through quality control or because of inherent vulnerability to higher temperatures. This paper describes the construction and instrumentation of a purpose-built dryer, using uniformly saturated cotton as a constant drying load. The machine incorporates both a heat pump cycle using R12 refrigerant and also controllable electrical resistance heaters. A liquid-line subcooler is included to remove heat from the system. Instrumentation includes measurements of wet and dry bulb temperature, refrigerant temperature and pressure, air and refrigerant flow rates, and thermal and electrical energy. Drying rate is monitored by weighing samples.     

Research on Marangoni condensation heat transfer for water and ethanol mixture vapor

A brass block was constructed as a test block to study the Marangoni condensation in this paper. The maximal temperature difference of the block surface on which pure steam condensed was 11^°C when the block was cooled by the normal temperature water. Regulations and modes of Marangoni condensation for mixture vapor with different mass fractions were studied when the speed of vapor was 0.3 m/s. As both temperature gradients and concentration gradients exist on the condensing surface, the experimental results indicate that the maximal heat transfer coefficient of mixture vapor can be 2.8 times that of pure steam when the Marangoni condensation of mixture vapor appears. The heat transfer coefficient of mixture vapor increases with the decrease of surface subcooling, and it appears a steep increase when the surface subcooling is small enough; the heat transfer flux has a maximum value as the surface subcooling rises; and the different modes of condensation are confirmed when the different ethanol concentration and different surface subcooling exist. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 505–514, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20035     

Experimental studies of low-temperature drying by dehumidification. Part 2—Experimental

Experiments are described in which several different types of cycles and dryers are compared, and it is shown that the best performance, in terms of both drying time and energy saving, is achieved by a recirculating cycle with a hybrid dryer with a heat pump dehumidifier and supplementary resistance heating.     

A new method for preventing HP from frosting

The utility of HP (heat pump) in winter is limited by the problem of frost. The authors discuss a method for preventing HP from frosting, i.e. air is dehumidified by solid adsorbent before entering the evaporator. Not only does air humidity reduce, but also air temperature rises for absorbing adsorbing heat. As a result, the frost problem is resolved, and performance of the HP is improved in winter. The adsorbent bed can be fixed behind the outdoor unit of HP. It is made of zeolite plates, with an active carbon coat. Both sides of each zeolite plate are coated with a very thin layer of a mixture of active carbon and sodium silicate. The active carbon coat (black adsorbent material) can absorb sunlight as a supplementary source of energy for electrical heater for desorption, thus saving electrical energy. Air pressure loss through the bed is so low that the HP fan need not be changed. Using a mathematical model simulation for the sorption process, the method is proven to be valid.     

太阳能液体除湿空调性能的实验研究

在对液体除湿机理研究的基础上，建立了太阳能液体除湿空调系统实验台，采用氯化钙溶液作为除湿剂，对系统的除湿性能进行了实验研究，对影响除湿的各主要因素进行了分析。     

基于泡沫铜翅片换热器的烟气水分回收实验研究

搭建了以泡沫铜翅片换热器为核心的烟气水分回收实验台,研究了冷却水进口温度、烟气雷诺数及烟气中水蒸气体积分数对该换热器水回收特性和换热特性的影响,基于实验数据,利用多元回归拟合得到对流换热的关联式,其预测值与实验值误差在6%以内。结果表明:水蒸气体积分数增大可以显著提升水回收特性,而冷却水进口温度及烟气雷诺数对其影响很小;冷却水进口温度与烟气雷诺数对换热效率的影响较大,冷却水进口温度与换热效率成反比,烟气雷诺数与之成正比,而水蒸气体积分数对其影响较小;实验获得的最大冷凝水产率为7.68 kg/h,最大冷凝率为56.94%,最大换热效率为96.95%。     

基于数据辩识算法的燃气热水锅炉运行特性研究

搭建了以泡沫铜翅片换热器为核心的烟气水分回收实验台,研究了冷却水进口温度、烟气雷诺数及烟气中水蒸气体积分数对该换热器水回收特性和换热特性的影响,基于实验数据,利用多元回归拟合得到对流换热的关联式,其预测值与实验值误差在6%以内。结果表明：水蒸气体积分数增大可以显著提升水回收特性,而冷却水进口温度及烟气雷诺数对其影响很小;冷却水进口温度与烟气雷诺数对换热效率的影响较大,冷却水进口温度与换热效率成反比,烟气雷诺数与之成正比,而水蒸气体积分数对其影响较小;实验获得的最大冷凝水产率为7.68 kg/h,最大冷凝率为56.94%,最大换热效率为96.95%。     

Condensation tests on glass samples for energy efficient windows

This article presents results from a pilot study comparing condensation patterns on small glass samples with different surface properties. Experiments were carried out on three commercial glass samples (clear float, TiO₂-coated and SnO₂-coated) to see how water condensed on the different surfaces. The experiments were carried out under a clear night sky in Uppsala, Sweden. It was found that the pane with the low-emittance coating stayed clean of condensation longer than the other two. In the morning, the water layer on the TiO₂-coated sample was smeared out so that it was possible to see through that pane, while the view through the other two was still blurred. The TiO₂ coating does not prevent condensation, but makes it easier to see through the water layer. These simple tests indicate noticeable differences between different surface materials and also that these effects can be studied by exposing small samples to a clear night sky without having to perform full scale tests.     

利用热网凝结水直接供暖

利用热网75℃凝结水直供热用户,因距离近,管网改造容易,中间热损失小,经计算分析,可以满足热用户需求,实际改造后运行良好,当年回收改造成本。     

空调冷凝水作为饮用水的回收利用

以美的MDV-JD22G/Y型挂壁式室内机为例,计算空调器冷凝水每小时产生量。从计算结果来看,空调器每日产生的水量足以提供人体每日所需水量。针对空调器的结构特点提出了冷凝水净化成饮用水的净化工艺。对净化后的冷凝水进行水质检验,各项指标符合国家标准。     

蒸汽凝结水闭式回收技术在炼油企业的应用

本文主要介绍了蒸汽凝结水闭式回收的主要方法及改造方案,对回收过程中存在的问题进行了分析,提出了解决这些问题的方法。并对回收所产生的效益和回收期进行了计算。结果证明,采用闭式技术回收凝结水用于中压除氧器,具有较好的经济效益和环境效益,是完全可行的。     

旁通管定压在实际工程中的应用

以临汾市一新建电厂为例分析了旁通管定压在供热系统中的应用。明确了定压点的连锁与控制,着重描述了在不同运行阶段系统动压线的调节,给出了合理的运行方案。     

Evaluation of rotary dehumidifier performance with and without heated purge

In this paper we evaluate the potential benefits from separating process air stream at the exit of rotary dehumidifier into two streams. One air stream, hot and humid, is called purge air stream and other is remaining process air stream. The remaining process air stream has a lower temperature and humidity ratio as result of separation of initial hot process air stream. It is found that as the purge angle increases the exit humidity ratio of remaining process air stream decreases up to a point where it reaches a minimum. The purge angle for which this occurs is named “effective purge angle”. The effective purge angles for different splits between adsorption and desorption side of the rotary dehumidifier, various regeneration temperatures, non-dimensional lengths and their corresponding optimum non-dimensional times are determined. An existing finite-difference model, developed by the authors of this paper, for simulation of desiccant wheel performance is extended to account for the separation of the process air stream at the exit of rotary dehumidifier and later mixing of purge air stream and outside air to form the regeneration air stream. The performance of desiccant wheel with heated “effective purge angle” is evaluated and compared with performance of the same wheel without purge angle at all. It is found, for all cases considered in this study, that having heated “effective purge angle” has overall positive effect on the performance of the rotary dehumidifier.     

水电站经济运行与评价管理初探

从流域梯级电站优化调度、厂内经济运行以及经济运行评价等几个方面,以构皮滩发电厂为例探讨了水电站经济运行所采取的措施。通过对影响发电耗水率、水量利用率、综合出力系数、弃水期负荷、水能利用提高率等指标的主要因素分解,确定反映水电站经济运行状况的综合指标,构建了水电站经济运行管理的评价指标体系,并对其应用情况进行了分析,以期为大型水电站的经济运行管理提供有益的参考。     

Parametric studies on a desiccant assisted air-conditioner

The desiccant assisted air-conditioners yield lower humidities in the conditioned space compared to the conventional systems. In this paper, the effects of design variables of the air-conditioner, namely supply airflow rate, compressor pumping capacity (compressor speed) and desiccant wheel speed on its performance are studied. It is found that an optimum wheel speed of about 17.5 rph exists at which both moisture removal capacity and COP are maximum.