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The application of evaporative cooling technique is getting more and more attention. The aim of the work is to propose a hybrid air-conditioning system. The hybrid system employs an indirect evaporative heat exchanger (IEHX) as a pre-cooling unit that is operated in tandem with conventional air handling unit. The present work has developed a numerical model by considering the pre-cooling effect of the IEHX. The IEHX is able to adopt the room exhaust air as its working air. In addition, the mathematical formulation for the conventional cooling coil has been developed to study the influence of the pre-cooling effect on the chilled water temperature. The calculated results have demonstrated the ability of the evaporative pre-cooling unit to cool and dehumidify the ambient air under humid tropical climates. The chilled water supply temperature can be also raised due the pre-cooling process. Consequently, an improvement on the coefficient of performance for the chiller is achieved. The hybrid system is able to obtain a potential energy saving as a result of the pre-cooling effect and the enhanced efficiency.

Battery thermal management is critical for the success of all electric vehicles due to the effects of extreme temperature on performance, reliability and lifespan of batteries. In this study, the three-dimensional model of a stagger-arranged battery pack was developed to investigate the effects of cooling channel size and air supply strategy on the thermal behavior of battery pack. The thermal resistance model of single irregular air passage was used to validate the numerical scheme. It was found that the appropriate cooling channel size of 1 mm for 18650 lithium-ion battery was achieved based on the three key parameters, namely, the maximum temperature, the space utilization and the energy efficiency factor. The numerical results illustrate that the best cooling performance can be achieved when airflow inlet and outlet are located on the top of battery pack. The cooling energy efficiency β decreases markedly with the increase of battery numbers along horizontal direction. As the ratio of the length of batteries along horizontal direction to battery diameter equals to 36.10, the lowest value of β is still acceptable. The analysis indicates that packing more battery along flow direction is an appropriate solution in terms of battery power density and cooling requirement.

The lithium ion battery has been widely applied in the fields of electric vehicles and electronic products due to its advantages of high power density, long lifespan and low self-discharging, etc. In this study, two lithium ion batteries are adopted to explore the effects of different thermal conditions on battery’s performance. One of thermal conditions makes battery close to adiabatic condition similar to the thermal condition of battery pack without any thermal management system. Another thermal condition is constant temperature condition employed to simulate the thermal condition of battery pack with thermal management system. The experimental results show that (i) next chargeable capacities of these batteries are dependent on the previous dischargeable capacities for all thermal conditions; (ii) dischargeable capacities of these batteries markedly decrease with the increase of the discharge rates under 20°C constant temperature condition; (iii) dischargeable capacities are independent on discharge rates under close to adiabatic condition because the obvious battery temperature rise can offset the adverse effects of higher discharge rates on battery’s performance. Although higher battery temperature is conductive to weaken or eliminate the adverse effects of higher discharge rates, excessively high temperature can also accelerate battery aging and easily cause battery thermal runaway, which indicates that it is necessary for battery pack with thermal management system to control thermal conditions of batteries.

This study focuses on the heat transfer between the vertical concentric tubes buried underground and the medium-deep rock-soil geothermal energy. The numerical simulation based on an in-house FORTRAN computation program was performed to analyze the mechanism of heat exchange underground. The program was shown to predict the test results of outlet water temperature and heat gain very well under the corresponding operating conditions when engineering data of an actual geothermal well were obtained to validate the numerical scheme. The effects of inlet water temperature and flow rate on the heat exchanger performance were also analyzed in detail. The comparison indicated that the present numerical scheme is able to predict the heat transfer performance of extremely long ground-coupled heat exchanger subject to various geothermal conditions.

The transport properties at low density are investigated in the framework of the kinetic theory of gases for five binary mixtures composed of CO2, N2, SF6, and CF4, which are of great interest to the electric power industry and are not available in the literature. The Lennard-Jones (12–6) potentials recommended in the literature are used to model the interactions between like molecules, and the Lorentz–Berthelot combining rules are employed to further describe the unlike interactions. The viscosity, binary diffusion coefficient, and thermal diffusion factor are computed for CO2–SF6, CO2–CF4, N2–SF6, N2–CF4, and SF6–CF4. The experimental data are available for the viscosity and diffusion coefficient of the studied systems over a much limited temperature range, and reasonable agreement is found between the experimental data and our calculated values. The new transport property values of the five binary mixtures are tabulated in the supplementary material, covering a very wide temperature range from 300 to 30 000 K.

Anthropogenic heat emission (AHE) influences the local energy balance and intensify the urban heat island (UHI) effect. An accurate calculation of the AHE can improve the precision of UHI predictions. However, reliable AHE calculations with high temporal and spatial resolution in domestic research is still lacking. Therefore, this study proposes an approach to estimate the dynamic AHE by integrating multi-source Internet big data and high-precision urban spatial data. First, we quantified the dynamic distribution of residents’ trajectories by tracking multi-stage Internet geographic location data, real-time traffic conditions of Xi’an city, supplemented by on-site drone monitoring. Then the parameters of cooling and the thermal load coefficient of building emissions, personnel cooling loads, and traffic densities were introduced. Finally, the temporal and spatial dynamic rules of the AHE were revealed. Results showed the AHE was subject to a large changing amplitude. The diurnal AHE values of 64% of the blocks ranged from 93 to 498 W/m2, especially in some core commercial areas, the value could reach above 1000 W/m2 during the peak stages. Compared with previous research, this study dynamically evaluates the temporal and spatial heterogeneity of the AHE under different emission scenarios with a short update cycle and high spatial resolution.

Urban building disposition plays an important role in determining local microclimate including air quality. Ancient cities normally have some special building dispositions to reduce the penetration of cold wind in winter, which, however, may impact adversely on air pollutant dilution today. This paper investigated the pedestrian-level air quality at a common building disposition in Chinese ancient cities, namely a U-type street canyon. On-site measurements were conducted comparatively at a U-type street canyon and a nearby open space in Xi'an China during January 2015. Three primary air pollutants (PM10, PM2.5 and NO2) as well as wind speed and direction, air temperature and relative humidity were measured continuously from 8:00 a.m. to 8:00 p.m. for a six-day period that covered both clean and hazy days. Pedestrian-level wind condition at the U-type street canyon is mostly independent of that above the canyon, where adverse dilution condition is clearly evident for pollutants. PM2.5/PM10 ratio at the street canyon reached up to 0.9, which is nearly twice that at the nearby observatory. Overall, air quality index (AQI) in the street canyon is, on average, higher by 20% than that at the open space. These findings suggest that this ancient design should be discouraged.

This study presented a pore-scaled numerical simulation on the melting phase change heat transfer of a phase change material (PCM) impregnated in open-cell metal foam. Idealized tetrakaidecahedron was selected as the representing unit cell (UC) to mimic the real foam microstructure and an assembly of tetrakaidecahedron UCs with six lines and three rows was built for computation. Phase change heat transfer in PCM and coupled heat transfer between PCM and metallic ligaments were directly simulated. To address the contribution of natural convection in the melting phase to the overall melting time and pore-scaled melting interface, natural convection in the interstitial fluid was modeled and compared with the conduction-dominated case. Results demonstrated that micro-foam can significantly accelerate the melting phase change rate and further enhancement was observed at pore scale when natural convection in the melting phase was triggered on.

With the construction of new villages in China, energy-saving technologies for rural buildings have been attracted extensive attention. According to the characteristic of severe cold climate in Hailar, Inner Mongolia, and the structure of rural residential buildings in Taohai Pasture and the energy use customs in these houses, the energy efficiencies of passive energy-saving technologies which are applied to demonstration houses in Taohai Pasture are analyzed. Based on BIM, the calculation models of three types of houses, including the demonstration house applied passive energy-saving technologies, the traditional house and the energy-saving standard model based on local rural residential energy-saving design standard, are established. Then energy simulation software is used to calculate dynamic heating loads of these houses. Furthermore some indexes such as heating load and annual energy consumption per unit building area are compared. The calculated results show that the heating load of the demonstration house in Taohai Pasture is decreased obviously through the passive energy-saving strategies of the thermal insulation of building envelopes, the effective setting of a solar room and the reasonable distribution of indoor functional zones. Compared to the annual heating loads of the traditional house and the energy-saving standard model, that of the demonstration house is reduced about 74.8 % and 28.9%, respectively. The investment increase of the envelope of the demonstration house can be recovered within 11.4 years through the reduction of annual energy use for heating.

The construction of eco-city is a hot spot nowadays, aiming to build harmony between human and nature. Ecological city is able to deal with the relationship between human and the environment, whose key point is to establish a comfortable outdoor thermal environment. To evaluate the built microclimate environment, a campus area located in Northwest China was selected. Different scenarios with extra greening, high albedo pavement materials, water body and their combinations were numerically analyzed through Universal Thermal Climate Index (UTCI) incorporated in the software ENVI-met V4.0. Results demonstrated that the scenarios with water body or high albedo materials was found to have little contribution to reduce UTCI, while the green scenario significantly reduced the UTCI peak (6.9 C) and also the duration (4.5 hours) of heat stress. The present study may be used as a guide for urban planning and construction for ecological city.

In recent years, a primary concern in the development of electronic technology is high heat dissipation of power devices. The advantages of unique thermal physical properties of graphite foam raise up the possibility of developing pool boiling system with better heat transfer efficiency. A compact thermosyphon was developed with graphite foam insertions to explore how different parameters affect boiling performance. Heater wall temperature, superheat, departure frequency of bubbles, and thermal resistance of the system were analyzed. The results indicated that the boiling performance is affected significantly by thermal conductivity and pore diameter of graphite foam. A proposed heat transfer empirical correlation reflecting the relations between graphite foam micro structures and pool boiling performance of Novec7100 was developed in this paper.

Increased artificial constructions due to urbanization absorb more solar radiation, making urban surface and air temperatures rise and affecting the energy performance of urban buildings and the human health. Many studies have reported that green facades and roofs, materials with high albedos can noticeably reduce building surface temperatures and cool the air in summer. However, little is known about the cooling effects and assessment of different mitigation strategies when they are adopted in a block scale. This study focuses on assessing and comparing the effects in the high-rise communities in Xi’an, China, which are a good representation of the city because they are composed of a high density of buildings, and they cover the majority of the current urban sprawl land. Simulations of three community prototypes through ENVI-met software were carried out in order to assess the mitigation techniques in terms of the ground surface, building surface, and vertical canopy air temperature decrease. The main techniques adopted were cool pavements, cool coating facades and roofs, green facades with ivy and green roofs with funkia and 15 cm substrates, and combinations of those. The statistical analysis results revealed that green roof can cool the roof more than the cool roof, while cool facade can cool the facade more than green facade. As to single mitigation strategy, the cool pavement have the most significant potential to decrease canopy air temperature. In general, the combination of different strategies had much more positive effects than single solution. These positive results indicate that the cooling strategies are urgently needed in the current urban construction to alleviate the urban heat island effect.

The modern development of electric vehicle requires higher power density to be packed into a battery pack. It is always expected that the battery can be arranged as much as possible, however, which leads to the serious thermal management issue due to the heat generation inside the battery packs. As extreme temperature affects performance, reliability, safety and lifespan of batteries, thermal management of battery system is critical to the success of all electric vehicles. The objective of this study is to explore the air cooling capability on the temperature uniformity and hotspots mitigation of a compact battery pack subject to various air flow paths, airflow rates. The numerical results show that the improvement of effective heat transfer areas between air-coolant and battery surfaces is able to obviously lower the maximum temperature and improve the maximum temperature difference in the densely-packed battery box.

Direct evaporative cooling systems usually involve the process of spraying water, which may form the drift of water droplets. In addition, the use of circulating water can also lead to the growth of bacteria and molding on the surface of the packing material, affecting the indoor air quality. To address these issues, this paper intends to propose an evaporative cooling method incorporated with hollow fiber membranes. The selective permeation membrane technology allows the membrane module to isolate air from water, which selectively allows only water vapor to pass through, preventing the droplets from entraining bacteria into the air. A mathematical model has been developed to theoretically investigate the heat and moisture transfer between water and air in a hollow fiber membrane-based evaporative cooling module. The governing equations for the pre-cooling IEHX were established and then solved by employing the COMSOL Multiphysics platform. This study validated the model by comparing its outlet air dry bulb temperature and relative humidity against experimental data acquired from literature sources. The numerical model showed good agreement with the experimental findings with maximum discrepancy of 7.0%. The validated model was employed to investigate the influences of the inlet air velocity, inlet air dry-bulb temperature, inlet air relative humidity and geometric parameters on the cooling effect of the evaporative cooling module. Simulation results indicated that the outlet air temperature is greatly affected by the relative humidity of the inlet air under constant inlet air temperature conditions. A higher inlet air relative humidity will result in a higher outlet air dry bulb temperature. In addition, the cooling effectiveness was reduced for a higher inlet air velocity. The design of the hollow fiber membrane-based evaporative cooling module was optimized based on the simulation study.

Rapid urbanization have increased the sensitivity of urban environment to extreme weather. To improve the deteriorating urban environment, the current situation of urban climate should be evaluated systematically and applied to the planning process. This study reports on the temporal and spatial variability of urban climate and introduces a method for constructing an urban climate map based on spatial statistical analysis of field measurement data. Taking Xi’an, a metropolis in northern China, as the case study, we first conducted a 3-year meteorological investigation, including air temperature, relative humidity, and wind speed in both summer and winter. Meanwhile, five indicators with potential impacts on urban climate were selected to describe the urban characteristics. Then, the geographic information system was applied to integrate the meteorological data and urban characteristic data in order to assign more meteorological data. Next, three types of meteorological single-factor and thermal comfort spatial distribution maps were derived. The k-means clustering analysis method was then employed to classify three types of meteorological factors into seven zones in horizontal spatial dimension. Finally, urban climate maps were generated. This study can help planners quickly distinguish urban climate-sensitive and valuable zones in order to make better strategies for future development.

This paper proposes a gravity heat pipe exchanger used for cooling the communication base station to replace the air conditioning in winter and transition seasons. Tests were made on the gravity heat pipe exchanger of DHHP 3000 produced by Harbin Dawnhappy Heat Pipe Technology Incorporated. The experiment was performed in order to study the effects of the inlet air flow rate, temperature and the exchanger inclination angle on cooling capacity and efficiency of the heat pipe exchanger. As the indoor and outdoor air flow rate are equal, the cooling capacity of heat pipe exchanger increases with the air flow rate and it also increases with the increase of indoor air temperature and with the decrease of outdoor air temperature; The cooling efficiency decreases with the increase of air flow rate and it gradually reduces with the outdoor air temperature increases from 2 °C to 18 °C. Among the ratios of indoor to outdoor air flow rate of 0.4 kg/s:0.5 kg/s, 0.4 kg/s:0.6 kg/s and 0.5 kg/s:0.6 kg/s, the cooling efficiency of 0.4 kg/s:0.6 kg/s achieves the highest value. In addition, as the inclination angle varies from 5° to 50°, the maximum cooling efficiency can be obtained at angle of 20°.

As a relatively new type of functional material, porous graphite foam exhibits unique thermophysical properties. It possesses the advantages of low density, high specific surface area, and high bulk thermal conductivity and could be used as the core component of compact, lightweight, and efficient heat exchangers. Effective thermal conductivity serves one of the key thermophysical properties of foam-based heat exchangers. The complex three-dimensional topology and interstitial fluids significantly affect the heat conduction in the porous structure, reflecting a topologically based effective thermal conductivity. This paper presents a novel geometric model for representing the microstructure of graphite foams with simplifications and modifications made on the realistic pore structure, where the complex surfaces and tortuous ligaments were converted into a simplified geometry with cylindrical ligaments connected between cuboid nodes. The multiple-layer method was used to divide the proposed geometry into solvable areas, and the series–parallel relation was used to derive the analytical model for the effective thermal conductivity. To explore heat conduction mechanisms at the pore scale, direct numerical simulation was also conducted on the realistic geometric model. Achieving good agreement with experimental data, the simplified geometric model was validated. The numerically simulated conductivity followed the simplified model prediction that the two geometries are equivalent from thermal aspect. It validates further that the simplified model is capable of reflecting the internal microstructure of graphite foam, which would benefit the understandings of the thermophysical mechanisms of pore-scaled heat conduction and microstructures of graphite foam.

A counter-flow regenerative indirect evaporative heat exchanger (RIEHX) was introduced and investigated. This paper aims to conduct an experimental study for the RIEHX to investigate the cooling performance under different operating conditions. The experimental prototype was able to adjust the inlet air flow rate and temperature. The thermal performance of the RIEHX was tested with variable inlet conditions. The experimental results have demonstrated that the supply air can be effectively cooled along the product air flow passages by transferring heat to the wet side of the RIEHX due to water evaporation. Under a constant inlet air velocity, the product air with a higher inlet temperature can obtain a larger temperature reduction. In addition, a lower air flow rate may enhance the cooling effect due to the increased contact duration between the air streams. The proposed system is able to improve the cooling effectiveness of the conventional plate-type indirect evaporative cooler.

Compared with traditional air-conditioning systems which aim at maintaining the designed indoor air temperature and humidity, radiant panels are capable to improve the human thermal comfort through the direct radiant heat transfer with occupants. Based on the Fanger's thermal comfort model, the simplified PMV (Predicted Mean Vote) model and calculation equation of cooling load are established. This paper analyzes the relationship between the human thermal comfort and indoor sensible cooling load, and explores the design and operation methods of indoor parameters. The model room with typical boundary conditions in the hot-summer and cold-winter zone of China is simulated and analyzed by Airpak. The widely accepted PMV and PPD (Predicted Percentage of Dissatisfied) indices are adopted to evaluate the indoor human thermal comfort. The parameters including the radiant surface temperature, the air supply temperature, the relative humidity and the ratio of the radiant surface areas are researched. The optimum indoor parameters in typical summer conditions are finally obtained, it is expected to provide a relevant reference for the design and operation methods subject to the radiant panel combined with fresh air system.

The system performance of a transcritical CO 2 heat pump is significantly influenced by the heat rejection pressure due to the nature of the transcritical refrigeration cycle. It has received wide attention in the scientific community. In this article, an experimental investigation of the optimal heat rejection pressure for a transcritical CO 2 heat pump water heater is presented. It is found that the optimal heat rejection pressure varies with gas-cooler outlet refrigeration temperature at different ambient temperatures. The further experimental results show that the Coefficient of Performance (COP) at the optimal heat rejection pressure decreases substantially with increasing gas-cooler outlet refrigeration temperature in a range from 25 to 45 °C. Based on the experimental data, a simple correlation of the optimal heat rejection pressure in terms of gas-cooler outlet refrigeration temperature is obtained. The analysis shows that the deviation of the correlation is within ±5%, and the predicted COP at the optimal heat rejection pressure is within 6%.

Cold acclimation is an important process by which plants respond to low temperature and enhance their winter hardiness. C-REPEAT BINDING FACTOR1 (CBF1), CBF2, and CBF3 genes were shown previously to participate in cold acclimation in Medicago truncatula In addition, MtCBF4 is transcriptionally induced by salt, drought, and cold stresses. We show here that MtCBF4, shown previously to enhance drought and salt tolerance, also positively regulates cold acclimation and freezing tolerance. To identify molecular factors acting upstream and downstream of the MtCBF4 transcription factor (TF) in cold responses, we first identified genes that are differentially regulated upon MtCBF4 overexpression using RNAseq Digital Gene Expression Profiling. Among these, we showed that MtCBF4 directly activates the transcription of the COLD ACCLIMATION SPECIFIC15 (MtCAS15) gene. To gain insights into how MtCBF4 is transcriptionally regulated in response to cold, an R2R3-MYB TF, MtMYB3, was identified based on a yeast one-hybrid screen as binding directly to MYB cis-elements in the MtCBF4 promoter, leading to the inhibition of MtCBF4 expression. In addition, another MYB TF, MtMYB61, identified as an interactor of MtMYB3, can relieve the inhibitory effect of MtMYB3 on MtCBF4 transcription. This study, therefore, supports a model describing how MtCBF4 is regulated by antagonistic MtMYB3/MtMYB61 TFs, leading to the up-regulation of downstream targets such as MtCAS15 acting in cold acclimation in M. truncatula.

As a new type of functional material, porous graphite foam exhibits unique thermal physical properties and geometric characteristics in heat transfer applications. It has the advantages of low density, high specific surface area, high porosity and high bulk thermal conductivity, which can be used as the core component of small, lightweight, compact and efficient heat sinks. Effective thermal conductivity serves one of the key thermophysical properties for foam-cored heat sinks. The complex three-dimensional topology and interstitial fluids significantly affect the heat conduction through such kind of porous structures, reflecting a topologically based effective thermal conductivity. This paper presents a novel geometric model for representing the microstructure of graphite foams, with simplifications and modifications made on the actual pore structure of graphite foam. For calculation simplicity, we convert the realized geometry consisting of complex surfaces and tortuous ligaments into a simplified geometry with circular ligaments joined at cuboid nodes, on the basis of the volume equivalency rule. The multiple-layer method is used to divide the proposed geometry into solvable areas and the series-parallel relations are used to derive the analytical model for effective thermal conductivity. To physically explore the heat conduction mechanisms at pore scale, direction numerical simulations were conducted on the reconstructed geometric model. Achieving good agreement with experimental data, the present analytical model (based on the simplified geometry) is validated. Further, the numerically simulated conductivities follow the model prediction, favoring thermally that the two geometries are equal. The present geometry model is more realized and capable of reflecting the internal microstructure of graphite foam, which will benefit the understandings for the thermo-physical mechanisms of pore-scaled heat conduction and micro structures of graphite foam.Copyright © 2016 by ASME

Many forms of electronic equipment such as battery packs and telecom equipment must be stored in harsh outdoor environment. It is essential that these facilities be protected from a wide range of ambient temperatures and solar radiation. Temperature extremes greatly reduce lead-acid based battery performance and shorten battery life. Therefore, it is important to maintain the cabinet temperature within the optimal values between 20 °C and 30 °C to ensure battery stability and to extend battery lifespan. To this end, cabinet enclosures with proper thermal management have been developed to house such electronic equipment in a highly weather tight manner, especially for battery cabinet. In this paper, the flow field and temperature distribution inside an outdoor cabinet are studied experimentally and numerically. The battery cabinets house 24 batteries in two configurations namely, two-layer configuration and six-layer configuration respectively. The cabinet walls are maintained at a constant temperature by a refrigeration system. The cabinet's ability to protect the batteries from an ambient temperature as high as 50 °C is studied. An experimental facility is developed to measure the battery surface temperatures and to validate the numerical simulations. The differences between the experimental and computational fluid dynamic (CFD) results are within 5%.

In household frost-free refrigerators, the air flow field is the most important factor that affects temperature distributions in chambers, while the performance of the supply-air openings for each chest determines the character of the flow field in the chest. Thus, it is necessary to perform experimental research on the air flow performance at the supply-air openings to improve the service performance, furthermore, to reduce the energy consumption of frost-free refrigerators. In this study, the airflow performance at the supply-air openings in a BCD-190W type household frost-free refrigerator was investigated. A transparent model was built based on similitude theory. The measurement system using 2-D Digital Particle Image Velocimetry (DPIV) technology and the proper tracer particles were adopted. The velocity distribution performance of typical rectangular supply-air openings in the refrigerator were measured. In addition, the problem in flow rate and location design of supply-air openings were presented on the basis of the analysis of the experimental results. The results show that DPIV can be applied to obtain the air flow performance at supply-air openings in frost-free refrigerators. Moreover, the structure of supply-air openings in each chest and the design of the supply-air tunnel resistance in cooling chamber should be improved.

Many forms of electronic equipment, of necessity, must be located in an outdoor environment. Such equipment in typical form may be battery packs or telecom-equipment. It is essential that these facilities be protected from a wide range of ambient temperatures and solar radiation. To this end, cabinet enclosures with proper thermal management have been developed to house such electronic equipment in a highly weather tight manner, especially for battery cabinet. Often the batteries are of a lead-acid construction which is known to be adversely affected by temperature extremes in terms of battery performance and life. Therefore, it is important to maintain the cabinet temperature ideally for ensuring battery stability and extending battery lifespan. In this paper, physical and mathematical models are established to investigate the flow field and temperature distribution inside an outdoor cabinet, which contains 24 batteries with two configurations of two-layer and six-layer respectively. The cabinet walls are maintained at a constant temperature by a refrigeration system and the ambient temperature is up to 50 °C according to the practical situation. The flow field and temperature distribution are analyzed with and without consideration of solar radiation. An experimental facility is then developed to measure the battery surface temperatures and to validate the numerical simulation. The differences between the CFD and experimental results are within 2%, which confirms the CFD model.

Room temperature magnetic refrigeration is a new highly efficient and environmentally protective technology. Although it has not been maturely developed, it shows great applicable prosperity and seems to be a substitute for the traditional vapor compression technology. In this paper, the concept of magnetocaloric effect is explained. The development of the magnetic material, magnetic refrigeration cycles, magnetic field and the regenerator of room temperature magnetic refrigeration is introduced. Finally some typical room temperature magnetic refrigeration prototypes are reviewed.

Staphylococcus aureus belongs to one of the most common bacteria causing healthcare and community associated infections in China, but their molecular characterization has not been well studied. From May 2011 to June 2012, a total of 322 non-duplicate S. aureus isolates were consecutively collected from seven tertiary care hospitals in seven cities with distinct geographical locations in China, including 171 methicillin sensitive S. aureus (MSSA) and 151 MRSA isolates. All isolates were characterized by spa typing. The presence of virulence genes was tested by PCR. MRSA were further characterized by SCCmec typing. Seventy four and 16 spa types were identified among 168 MSSA and 150 MRSA, respectively. One spa type t030 accounted for 80.1% of all MRSA isolates, which was higher than previously reported, while spa-t037 accounted for only 4.0% of all MRSA isolates. The first six spa types (t309, t189, t034, t377, t078 and t091) accounted for about one third of all MSSA isolates. 121 of 151 MRSA isolates (80.1%) were identified as SCCmec type III. pvl gene was found in 32 MSSA (18.7%) and 5 MRSA (3.3%) isolates, with ST22-MSSA-t309 as the most commonly identified strain. Compared with non-epidemic MRSA clones, epidemic MRSA clones (corresponding to ST239) exhibited a lower susceptibility to rifampin, ciprofloxacin, gentamicin and trimethoprim-sulfamethoxazole, a higher prevalence of sea gene and a lower prevalence of seb, sec, seg, sei and tst genes. The increasing prevalence of multidrug resistant spa-t030 MRSA represents a major public health problem in China.

This paper evaluates the economy of gravity heat pipe exchanger used for cooling communication base station to replace air conditioning in winter and transition seasons. The experimental data were analyzed, which proved that the gravity heat pipe exchanger can reduce running time and operating cost of air conditioning system. Based on the practical applications, the yearly cooling loads of a typical communication base station were calculated for five cities which represent the typical weather conditions of the five climatic zones in China. The results showed that the energy saving by using the gravity heat pipe exchanger is significant. The annual electricity-saving rate is the highest in Kunming, about 48.6%, while the annual electricity-saving rate is the lowest in Guangzhou, about 18.7% among the five climatic zones.