The Selection of Cooling Systems of Giant Hydro-Generators

The selection of cooling system for hydro-generator in Ertan Hydropower Station is reviewed in this paper. The new viewpoint on air-cooled system of hydraulic generator of recent years is analyzed and described. That is, "Full air-cooled system is always preferred to

The effects of portable cooling systems on thermal comfort and work performance in a hot environment

There are some special spaces in which there is no air conditioning or the people are in move,thus exposing people to a hot environment.In this study,portable cooling systems were proposed and their effects on thermal comfort and work performance were investigated at an air temperature of 32°C.Four conditions were established:cool air towards breathing zone(A),chest and back cooling(B)#combined cooling(C)and no cooling(D).Twenty-eight subjects were exposed to the four conditions in a counterbalanced order.During each exposure they performed tasks and made subjective assessments,while multiple physiological parameters were measured.Compared with no cooling(D),cool air towards breathing zone(A)and chest and back cooling(B)improved work performance by 17.5%and 19.25%,respectively,while decreased the subjects'thermal sensation,skin temperature,and heart rate.When the two cooling systems were combined(C),larger improvements in thermal comfort and work performance were achieved than no cooling(D);the mean thermal sensation rating decreased from 2.4 to 0.7;work performance increased by up to 33%,and physiological parameters including skin temperature,pulse,heart rate and salivary alpha-amylase significantly decreased.The present results suggest that the proposed portable cooling systems could maintain thermal comfort and work performance in a hot environment,while potentially improve air quality for some special spaces.

Evaporative cooling of ^(87)Rb atoms into Bose-Einstein condensate in an optical dipole trap

We create a Bose-Einstein condensate （BEC） of 87Rb atoms by runaway evaporative cooling in an optical trap. Two crossed infrared laser beams with a wavelength of 1064 nm are used to form an optical dipole trap. After precooling the atom samples in a quadrupole-Ioffe configuration （QUIC） trap under 1.5 #K by radio-frequency （RF） evaporative cooling, the samples are transferred into the center of the glass cell, then loaded into the optical dipole trap with 800 ms. The pure condensate with up to 1.5× 10^5 atoms is obtained over 1.17 s by lowering the power of the trap beams.

Evaporative cooling rubidium atoms with microwave radiation

We report the experimental achievement of ^（87）Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency（RF） induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the ^（87）Rb atoms to transit from the ground-state hyperfine state ｜F=2,m_F= 2〉to ｜F=l,m_F=1〉.Compared with RF-induced evaporation,^（87）Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the ｜F=1,m_F=1〉state being pumped back into the trapping ｜F=2,m_F=1〉state.

PARAMETERS OF WATER CIRCULATION NETWORK FOR A DISTRICT HEATING AND COOLING SYSTEM

In a district heating and cooling system, i.e. Beijing combined heating cooling and power (CHCP) system studied here, the high temperature water generated by two cogeneration plants circulates through a network between the plants and heat substations. At heat substations, the supply water of high temperature from the network drives absorption chillers for air-conditioning in summer and meets space heating demands in winter or domestic hot water demands by heat exchangers in the whole year. The parameters, i.e. supply/return water temperatures in the network, have a great impact on primary energy consumption (PEC) of the absorption chillers, circulation pumps and domestic hot water (DHW), which is studied in this paper.

Energy efficiency of small buildings with smart cooling system in the summer

In this paper,a novel cooling control strategy as part of the smart energy system that can balance thermal comfort against building energy consumption by using the sensing and machine programming technology was investigated.For this goal,a general form of a building was coupled by the smart cooling system(SCS)and the consumption of energy with thermal comfort cooling of persons simulated by using the EnergyPlus software and compared with similar buildings without SCS.At the beginning of the research,using the data from a survey in a randomly selected group of hundreds and by analyzing and verifying the results of the specific relationship between the different groups of people in the statistical society,the body mass index(BMI)and their thermal comfort temperature were obtained,and the sample building was modeled using the EnergyPlus software.The result show that if an intelligent ventilation system that can calculate the thermal comfort temperature was used in accordance with the BMI of persons,it can save up to 35%of the cooling load of the building yearly.

Analytic estimation and numerical modeling of actively cooled thermal protection systems with nickel alloys

Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and numerical modeling are performed in this paper to investigate the behavior of an actively cooled thermal protection system. The analytic estimation is based on the electric analogy method and finite element analysis（FEA） is applied to the numerical simulation. Temperature and stress distributions are obtained for the actively cooled channel walls with three kinds of nickel alloys with or with no thermal barrier coating（TBC）. The temperature of the channel wall with coating has no obvious difference from the one with no coating, but the stress with coating on the channel wall is much smaller than that with no coating. Inconel X-750 has the best characteristics among the three Ni-based materials due to its higher thermal conductivity, lower elasticity module and greater allowable stress. Analytic estimation and numerical modeling results are compared with each other and a reasonable agreement is obtained.

Investigations and experiments of a new multi-layer complex liquid-cooled mirror

This paper describes a new multi-layer complex liquid-cooled Si mirror with 3 cooling ducts in Archimedes spirals. Utilizing the ANSYS program, the structure of the mirror is optimized and the thermal deformation model of the mirror is simulated. The simulation results show that the mirror has the following advantages: very small amount of surface deformation, uniform distribution of temperature and surface deformation, and fast surface shape restoration. The results of the experiments of thermal deformation and the surface restoration are accurately mapped to the simulation results.

Comparison of laser performance of electro-optic Q-switched Nd:YAG ceramic/single crystal laser

An electro-optic Q-switched Nd：YAG ceramic laser operating at kHz repetition rate was demonstrated. Thermal induced lens＇ focus of ceramic rod was measured and compensated by piano-convex cavity structure. Depolarization loss at different output powers was measured in Nd：YAG single crystal and ceramic lasers. High-energy high-beam-quality laser pulse output was obtained in both laser structures. Pulse energy of about 20 mJ and pulse width of less than 12 ns were achieved, and the average power reached 20 W. The divergence of output laser beam was less than 1.2 mrad, and the beam propagation factor M^2 was about 1.4.

Contrastive study of two SESAMs for passive mode-locking in Nd:YVO_4 laser with low pump power

Two semiconductor saturable absorber mirrors （SESAMs）, of which one is coated with 50% reflection film on the top and the other is not, were contrastively studied in passively mode-locked solid-state lasers which were pumped by low output power laser diode （LD）. Experiments have shown that reducing the modulation depth of SESAM by coating partial reflection film, whose reflectivity is higher than that between SESAM and air interface, is an effective method to get continuous wave （CW） mode-locking instead of Q-switched mode-locking （QML） in low power pumped solid-state lasers. A simple Nd：YVO4 laser pumped by low power LD, in which no water-cooling system was used, could obtain CW mode-locking by the 50% reflector coated SESAM with average output power of ～ 20 mW.

Post-harvest storage of lime fruits (Citrus aurantifolia) following high humidity and low temperature in a modified brick wall cooler

The use of a modified brick wall Evaporative Cooling Chamber(ECC)for extending the shelf life of limes(Citrus aurantifolia)was compared with ambient storage.The shelf life inside of the ECC was extended by five to twenty days relative to ambient storage.The inside temperatures were about 4-6℃less than the ambient temperatures,and humidity was about 10%-20%higher.Study was conducted to check the weight loss and freshness of lime fruits,and data were observed daily.Weight loss in limes kept inside the chamber for ten days was 1.8%and in ambient conditions it was around 9.8%.The color of the fruit changed to yellowish inside the ECC and the control which was kept outside became unmarketable.ECC storage did not adversely affect fruit firmness,or the percentage of soluble solids or titratable acidity of the juice.The modified ECC does not require mechanical or electrical energy input and can be constructed with locally available material by unskilled labour.