Spray Characteristics of a Two Phase Air water Nozzle for Indirect Evaporative Cooling

We present a two phase air water nozzle that can be applied to indirect evaporative cooling to improve the heat transfer efficiency of indirect evaporative coolers by improving the uniformity of the water film on the surface of the heat exchanger. The spray characteristics of a nozzle with a fan shaped orifice at various air and water pressure conditions was studied. The spray cone angle, the air water mass flow rate, and the relationship between the mass flow rate and the air water pressure ratio were obtained. The best air water pressure ratio and spray cone angle were also found.     

Photosynthetic characteristics of subtending leaves and their relationships with soybean pod development under heat,drought and combined stresses

Soybean is usually grown under rain-fed conditions, and long-term drought stress often occurs with short-term heat stress. This study aimed to investigate changes in the photosynthetic characteristics of subtending leaves and their relationships with pod development under short-term heat, long-term drought and their combined stresses. Short-term heat stress lasted for 5 days began at R5 stage, and long-term drought stress lasted from R5 stage until maturity, respectively. No significant effect was observed on pod development under short-term heat stress alone due to unaffected net photosynthetic rate after treatment and PSII recovery after the heat stress release. Except that the reduction of sucrose content had been brought forward from 12 to 5 days after treatment under combined stresses, application of combined stresses caused similar responses to long-term drought stress alone on the photosynthetic characteristics of subtending leaves and pod development, but more pronounced under combined stresses. Reduced pod weight and seed weight per pod under long-term drought stress alone or combined stress due to a decrease in the net photosynthetic rate and production of sucrose and starch, especially after 19 days of treatment. Findings from this study demonstrate that under combined stress, long-term drought stress had a dominant effect on the photosynthetic performance of subtending leaves and pod development over short-term heat stress; moreover, even short-term heat stress also exacerbates the negative effects of long-term drought stress.     

Study on flammability and flame-retardant mechanism of modified asphalt for tunnel pavement synergisticly flame retarded by BFR-Ti and ZB

Tunnel fire resistant asphalt can be prepared by mixing SBS modified asphalt and BFR-Ti/ZB. The combustion performances of the SBS modified asphalt/BFR-Ti/ZB and the synergism mechanism of the BFR-Ti and ZB are studied systematically through different methods, such as oxygen index (LOI) method, density of smoke, cone calorimetry, thermogravimetric analysis, etc. The result indicates that compared with SBS modifiedasphalt/BFR-Ti, BFR-Ti/ZB has synergistic effect which can make smoke density, heat release rate(HRR), mass loss rate(MLR) and effective heat of combustion(EHC) of SBS modified asphalt/BFR-Ti/ZB systems significantly decrease while the oxygen index of the SBS modified asphalt/BFR-Ti/ZB and the practice carbon content increase. SBS modified asphalt/BFR-Ti system has significant endothermic-antiflaming mechanism and condensed phase flame-retardance character. SBS modified-asphalt / BFR-Ti/ZB is based on the condensed phase flame-retardance mechanism while with synergistic flame-retardance and endothermic-antiflaming mechanism.     

谷物呼吸热值测定研究

谷物呼吸热值测定是粮食通风散热课题的核心问题.本文利用气体分析仪和恒温水槽测定谷物呼吸对氧气的消耗量和二氧化碳的生成量,作者首次提出了同时考虑有氧呼吸和无氧呼吸两因素,对呼吸方程进行配平,从而由呼吸生成物与呼吸反应物之间生成??值之差来精确计算出呼吸热. 数据处理全过程由微机完成.     

Heat Stress Effects are Stronger on Spikelets Than on Flag Leaves in Rice Due to Differences in Dissipation Capacity

Rice is most sensitive to heat stress at the flowering stage, with different degrees of heat damage in spikelets and leaves. To investigate the heat damage in spikelets and flag leaves, two rice genotypes, N22 (heat‐tolerant) and GT937 (heat‐sensitive), were subjected to a heat‐stress treatment (40 °C for 15 days). The results showed that more damaging was found in spikelets than in flag leaves and the heat stress significantly decreased the seed‐setting rate by 12.41 % in N22 and by 65.02 % in GT937. However, the difference in the net photosynthetic rate of the flag leaf between heat‐stressed and control was not significant. Moreover, the difference of temperatures in spikelets and flag leaves was attributed to the differences in heat dissipating. Under heat stress, the transpiration rate was significantly higher in flag leaves than in spikelets, and the temperature in flag leaves were at least 4 °C cooler than in spikelets. Although the spikelet temperatures did not differ significantly between the two genotypes under heat stress, spikelets of GT937 were more severely damaged than those of N22, which might result from the differences in the antioxidant capacities between genotypes. Results showed that little difference of superoxide dismutase, peroxidase and catalase activities of spikelets was found in N22, while significant reduction was found in GT937 under heat stress, compared with control. These results suggest that organ temperature is controlled mainly by transpirational cooling, and that heat stress is an indirect result of oxidative stress, rather than a direct result of heat damage.     

Thermodynamic Analysis of River Water Fouling on Constant Wall Temperature Tube of Small Diameter

In order to improve utilization of cold and heat source from river, turbulence theory and entropy generation theory were adopted to analyze the effect of fouling on convective heat transfer performance in small diameter tube of constant wall temperature.It is found that the entropy generation caused by conduction of fouling plays a more important role in total entropy generation of heat transfer process through a duct than that in cveast rate of caused by temperature difference.The entropy generation caused by viscous flow is more than the entropy generation caused by temperature difference in flow with bigger Reynolds and small radius.The increase rate of entropy generation monotonically increase with Reynolds and the generation process of fouling resistance.Thereafter, the effect of fouling resistance on the heat transfer performance of water source heat pump heat exchanger should be paid more attention, when river water are used as the cold and heat source of heat pump.     

热管管外结冰过程研究

通过对热管制冰传热过程的理论分析,得出影响结冰速率的主要因素是热管的温度与半径.建立了管外结冰一维传热模型,分别以半径和时间为步长对结冰速率进行迭代求解,并利用半径微元法得出了不同温度以及不同圆管半径下的制冰速率曲线.与试验结果相比,所得理论模型能够较好地与其吻合.     

热应激小鼠附睾组织HSP70表达的研究

利用化学恒温培养箱对小鼠实施42℃1h/d的热应激处理,建立持续的全身热应激动物模型。在热应激持续到8d、13d、21d和35d时,颈椎脱臼处死对照组和热应激组小鼠,应用改良巴氏染色法检测附睾精子畸形率,免疫荧光组织化学和蛋白质印迹分析的方法检测附睾组织HSP70的表达。结果显示：热应激组小鼠附睾精子畸形率随着热应激持续时间的延长而升高,且显著（P<0.05）高于对照组;对照组小鼠附睾组织HSP70呈极强表达（+++）,而热应激组小鼠附睾组织HSP70的表达随着热应激持续时间的延长而减弱,当热应激持续到35d时呈极弱的表达（±）。结果表明：热应激损伤了附睾的功能,使附睾精子畸形率增加;附睾内HSP70为非热诱导型,HSP70可能在附睾精子的成熟过程发挥特殊的作用。     

苏北地区日光温室能量分配动态研究

为了进一步提高日光温室保温性能,减轻温室内低温寡照灾害发生,以苏北（徐州）番茄日光温室为研究对象,利用采集的2010年12月-2011年4月温室小气候数据及番茄发育数据,根据日光温室小气候形成的物理过程与机理,系统研究了冬春季节不同天气类型及不同叶面积指数对温室能量分配的影响。结果表明：日光温室内潜热、显热随着室内总辐射量的改变而发生变化,阴天以显热消耗为主,潜热消耗量全天低于显热;晴天日光温室内用于作物蒸腾的能量显著多于阴天,阴天室内外贯流传热消耗的能量远远多于晴天;随着叶面积指数增大,到达地面的太阳辐射减少,地面升温慢,室内空气与地表的显热交换量减少,同时室内空气与墙体的显热交换增加。本研究结果可为温室的结构优化及冬春季节日光温室管理提供科学依据。     

以热量指数表示北疆棉区棉花延迟型冷害指标的研究

应用乌兰乌苏农业气象试验站棉花试验的生育期、产量及旬气温资料,计算出棉花不同播期和不同生长阶段的热量指数,研究分析不同播期棉花产量、霜前花率与棉花不同生长阶段的热量指数之间的关系发现:1)随播种期推后,棉花生长前期热量指数明显增加,而棉花生长后期的热量指数则呈现出明显的下降趋势。2)现蕾—开花阶段的热量满足状况很好,热量指数稳定。3)分期播种的单产与棉花生长后期的热量指数具有很好的线性关系,霜前花率也与棉花生长后期的热量指数关系密切,生长后期的热量指数变化对棉花品质的影响较产量更加敏感。4)以减产幅度为标准,在棉花开花期以前热量充足的情况下,后期生长热量指数低于64为一般延迟型冷害年指标,低于61.8为严重延迟型冷害年指标。5)以霜前花率为标准,在棉花开花期以前热量充足的情况下,后期生长热量指数低于 70.9 会出现一般冷害年,低于63.2,会出现严重冷害年。     

地铁用间接蒸发冷却器换热性能影响因素

为解决地铁站冷却塔设置难题,提出了一种采用低速电机驱动旋转布水装置的间接蒸发冷却器,在两种布置方式下,对其换热性能进行了单因素实验,并运用正交实验法对较优布置方式下影响换热器换热的因素进行了分析。结果表明：两种布置方式下,喷嘴与蒸发冷却器的间距、两组换热管束间距均存在最佳值,喷嘴双侧旋转布水优于单侧旋转布水;换热器平行气流布置且喷嘴双侧旋转布水为较优布置方式,此时,换热器换热量随喷水量、转速、空气速度、冷却水进口温度的增加以及喷水温度、空气温度的降低而增大,其中,冷却水进口温度对换热器换热影响最为显著,其他因素对其换热的影响从主到次顺序为：喷水量、空气温度、空气速度、喷水温度、转速、冷却水流量。     

A Theoretical Study on Thermal Dynamics Model and the Dehumidification Capacity of Hybrid Desiccant Cooling System with Condensation Heat Recovery

The structure and energy conservation characteristics of hybrid desiccant cooling system with condensation heat recovery are introduced briefly. Based on the first and second law of thermodynamics, a system thermodynamic model is established and the solution process given in a diagram. The dehumidification capacity is calculated under different exergy efficiency and indoor sensible heat conditions. The calculation results show that the desiccant wheel barely can compensate for the humidity load of outdoor air under with a ventilation rate of providing fresh air once per hour; when the fresh air rate of ventilation is limited to 0.5 times per hour, however, the desiccant wheel possess sufficient capacity under relatively large wheel exergy efficiency and high sensible heat load.     

Pressure Drop and Evaporative Heat Transfer Characteristics of Air-water Bubbling Flow

A new kind of evaporative heat transfer experiment for the cooling process of condensers is conducted. The test coil is immersed in an air-water bubbling layer. The air-water two-phase flow passes through the heating tubes of the coil. Due to the motion of the air bubbles in the water, a thin water film forms on the surface of the heating tubes. As the air bubbles passing by the tubes the water is evaporated into the air. The tubes of coil reject heat to the water film, and the evaporation of the water film then rejects heat to the air bubble stream. This heat transfer mode significantly increases the heat transfer coefficient between tubes and air. The consumption of the power of a water pump can be decreased. Moreover, the airflow rate required is less than that of an air-cooled condenser.The pressure drop of air through air-water bubbling layer and the heat transfer between the tubes and water are experimentally investigated in the paper. The results show that the factors affecting the pressure drop and the heat transfer coefficient involve the pore geometry of sieve plate, the height of the air-water bubbling layer, the air flow rate through the sieve plate and the heat flux of tubes. The heat transfer coefficient between tube and water is two times larger than that of falling film of water on the outer surface of tube.     

蝴蝶兰不同耐热性品种幼苗对高温胁迫的生理反应

摘要：分别在25℃、35℃、40℃各处理2天,测定了耐热性存在差异的两个蝴蝶兰品种幼苗的生理指标变化。结果表明,随着温度的上升,两品种的相对电导率和丙二醛含量(MDA)均不断增加,而耐热性强的品种的相对电导率和丙二醛含量增幅明显小于耐热性弱的品种;随着温度的上升,两品种的超氧化物歧化酶(SOD)、过氧化物酶(POD)活性、可溶性蛋白含量均为先升而后降,但耐热性强的品种的SOD、POD活性、可溶性蛋白含量增幅明显大于耐热性弱的品种,而降幅明显小于耐热性弱的品种;随着温度的上升,两品种的脯氨酸和可溶性糖含量均持续增加,而耐热性强的品种的脯氨酸和可溶性糖含量增幅明显大于耐热性弱的品种。由此得出,耐热性强的品种具有较强的细胞渗透调节能力以及消除活性氧伤害的能力,是其耐热性较强的生理基础之一。     

浙南茶树高温热害日数的气候变化特征

为了了解浙南茶树高温热害程度,更好地为农业生产服务。根据浙南1971—2017年各县（市、区）逐日平均气温、最高气温、平均相对湿度观测资料,根据茶树高温热害气象指标统计浙南茶树高温热害日数,采用趋势分析方法和Mann-Kendall检验,分析浙南茶树高温热害的时空分布特征和趋势变化。结果表明：浙南茶树高温热害日数年均5.2 d/a,以丽水最多(12.9 d/a),庆元最少(1.1 d/a),7月下旬发生高温热害日数最多。浙南茶树高温热害日数呈显著上升趋势,气候倾向率1.9 d/10 a,2000年发生突变,21世纪初增多最为明显。丽水是浙南茶树高温热害最明显的区域,气候倾向率4.7 d/10 a,1993年突变转折,2003年开始显著增加,茶树遭受高温热害的几率明显增大。     

Influence of heat storage mode of domestic hot water on the performance of ground heat exchanger in ground-source heat pump system

The vertical U-tube ground-coupled heat pump system provides cold and heat for the controlling of indoor environment. Under the air-conditioning condition, the vertical U-tube ground-coupled heat pump system with heat recovery can provide domestic hot water. The influence of supplying domestic hot water on the heat transfer performance of ground heat exchangers is different under different operating modes in summer and winter. Through a project design of ground-source heat pump system, the influence of supplying domestic hot water under heat storage mode on the heat transfer performance of ground heat exchangers in summer and winter is respectively analyzed. The dynamic performance of heat exchangers under different working conditions is analyzed, and through numerical calculation, the heat transfer performance parameters of ground heat exchangers under different operating modes are obtained. From the calculation results, the adjusting methods based on the load characteristics of this project represent.     

直接接触式换热器传热性能优化

建立了以容积换热系数为目标函数,工质流率U₀、喷头喷孔直径d_i、导热油液位高度Z为决策变量的直接接触式换热器性能优化模型,同时进一步将液滴群行为与传热协同关系作为约束条件引入优化模型中,重点分析该约束条件对优化过程及结果的影响。运用遗传算法对原模型和补充模型进行了优化分析,结果表明：原模型优化后的容积换热系数达到了初始值的6.7倍;而补充模型最优值的迭代次数比原模型减小了约55%,同时最优值比原模型提高了0.3%。所以该约束条件不仅提高了迭代速率,还提高了寻求全局最优值的概率,使得最优解更逼近全局最优值。     

A Thermodynamic Criteria for Evaluation of Heat Exchanger Performance

The concept of loss rate of available energy was introduced for evaluating heat exchanger performance. At the same time, the general expression of loss rate of available energy was obtained for heat exchangers of several typical. And NL criteria was recommended for evaluation of the loss rate of available energy of heat exchanger. Then. the influences of inlet temperatures ratio, heat capacity ratio of fluids, the number of heat transfer units and flow patterns of heat exchanger on ,VL criteria were also discussed.     

Energy efficiency analysis on intermittent operation based on life cycle cost in the vertical ground source heat pump system

Intermittent operation can affect the heat exchange performance of the vertical ground source heat pump system, thereby affecting life cycle cost (LCC) of the ground source heat pump system. The simulation analysis on the hourly load of an office building is implemented by using the DeST software.The heat exchange model of vertical ground heat exchanger pipe-group and energy consumption model of per part of heat pump system are established. Through the comparison between calculation results of continuous operation for 15 years and calculation results of intermittent operation 15 years of the heat pump system, it can be concluded that the LCC value of intermittent operation decreased by 13.45%,relative to the LCC value of continuous operation, and the average energy saving rate of intermittent operation mode is 17.20% in the entire life cycle. Intermittent operation mode can effectively improve energy efficiency of the ground source heat pump system and reduce the LCC value.     

Experimental Study of Flow and Heat Transfer in Heat Exchanger with Small Channels

The experimental study of the flow resistance and heat transfer characteristics are conducted for water and ethylene glycol solution (66% Wt) flowing in the heat exchanger with small rectangular microchannels . The heat exchanger having the channels of 0.4 mm in width, 2.0 mm in height, and 20 mm in length is heated by a hearing rod at the bottom surface, the upper and two side surfaces are adiabatic. During experiments, the Reynolds number are ranged from 2 to 2 500. The experimental results show that the flow friction factor decreases and Nusselt number increases with increasing Reynolds number for water and ethylene glycol solution. At a fixed Reynolds number, the Nusselt number for ethylene glycol solution with larger Prandtl number is greater than that for water. Meanwhile, the correlations of flow resistance and heat transfer in the heat exchanger with small channels are obtained for engineering application.