Thermal performance of a parallel earth air-pipes system

In the present analysis the thermal performance of a parallel earth air-pipe system has been evaluated in terms of annual heating and cooling potential. The influence of the pipes on each other's thermal performance has been considered. The effect of seasonal variation of environmental parameters (ambient temperature, solar radiation, relative humidity, earth temperature etc.) has been considered. The results are obtained for the hot-dry climate of Jodhpur and the composite climate of Delhi. From the various possible earth surface treatments to increase the effectiveness of earth storage systems for air conditioning purposes, the results are presented for wet-shaded earth surface conditions, the most effective earth surface treatment for the climate considered. Thermal performance of the parallel air-pipe system is evaluated for the two cases. In the first case, inlet air temperature to the pipes is taken to be the hourly mean of the ambient air temperature of the average day of each month, and, in the second case, the inlet air temperature is taken to be equal to that of a conditioned room whose set-point temperature varies from month to month.     

Performance of earth air tunnels

Corresponding to the annual variation of the meteorological data for the year 1974 at New Delhi, a study of the annual variation of the ground temperature distribution has been carried out for different surface conditions. At a depth of around 4 m the temperature remains almost constant in all the cases; it is maximum (～ 53°C) for a dry glazed black surface and minimum (～ 17-3°C) for a wet shaded surface, respectively. An earth air tunnel dug at this depth provides heating/cooling to the air flowing inside it during winter/summer. We have carried out a parametric study of the performance of such tunnels in terms of the heat gain/loss by air flowing through them.     

Parametric and experimental study on thermal performance of an earth–air heat exchanger

In the present paper a quasi‐steady state mathematical model is developed to predict the outlet air temperature and monthly heating and cooling potentials of an earth–air heat exchanger. Monthly values of heating and cooling potentials are estimated by rigorous experimentation throughout the year for composite climate of New Delhi. The uncertainty values are calculated for each month; for December the value is 4.9%. It is observed that there is an 8.9 and a 5.9°C temperature rise and fall during winter and summer due to the earth–air heat exchanger buried at a depth of 1.5 m underground. The correlation coefficient, root mean square of percentage deviation, reduced chi‐square and mean bias error have been computed for each month. The values are 1, 3.0%, 0.8 and ?0.63 for December. Statistical analysis shows that there is fair agreement between theoretical results and experimental observations for each month. Monthly values of heating and cooling potentials have also been predicted for other climatic conditions in India namely Jodhpur, Chennai, Mumbai and Kolkata. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of different earth surface treatments on the thermal performance of a room coupled to an earth-air tunnel

The thermal performance of a normal size room (4 m × 3 m × 3 m) connected to an idealized earth-air tunnel has been analysed interms of heating degree-hours (base 18°C) and cooling degree-hours (base 30°C). The effects of various earth-air tunnel parameters on the heating degree-hours and cooling degree-hours have been studied. The effects of various treatments of the earth surface over the tunnel have been analysed for three different climates (namely hot-dry, hot-humid and cold-dry) prevalant in India. The earth-surface treatments for hot-dry and hot-humid climates include shading and wetting of the earth surface, and for the cold-dry climate, the surface treatments considered are blackening and glazing of the earth surface.     

Effect of solar absorptivity and emissivity of exterior surfaces on the thermal performance of a building

The effects of the solar absorptivity and the thermal emissivity of exterior building surfaces on the indoor air temperature of a one room building are evaluated in terms of the discomfort index. The thermal performance of the building has been investigated for four different climates prevalent in India, namely, composite (New Delhi), hot and dry (Jodhpur), cold and humid (Srinagar), and cold and dry (Leh). The results confirm the common-sense view that the building surface should have low solar absorptivity and high thermal emissivity in hot climates and high solar absorptivity and low thermal emissivity in cold climates for indoor thermal comfort conditions.     

Optimum length of underground tunnel and corresponding annual heating/cooling potentials

Dimensionless optimum lengths of an underground tunnel, for which annual heating potential (HPD) and annual cooling potential (CPD) per unit tunnel length are maximum, have been obtained in terms of dimensionless parameters. The effect of different earth-surface treatments (shading, wetting, blackening and glazing) over the tunnel on the optimum tunnel length and corresponding values of HPD/CPD for three climates, namely hot-dry, composite and cold-dry, prevalent in the country have also been evaluated.     

Thermal performance of roof evaporative cooling and floor coupled evaporatively cooled underground water storage tank systems

The thermal performance of a room with two indirect evaporative cooling systems (operating independently and jointly) is analysed. The two evaporative systems considered are a water-film roof evaporative cooling system, and an underground water storage tank beneath the floor of the room. The water in the tank is evaporatively cooled through a suitable aeration system. The performance of the room is analysed in the hot-dry climate of Jodhpur and the composite climate of Delhi. It is found that the underground water storage system is marginally better than the roof evaporative cooling system for the Jodhpur and Delhi climates. A detailed parametric performance analysis of the room has also been carried out.     

Experimental investigations of a small-scale solar-assisted absorption cooling system

The present study deals with a small-scale solar-assisted absorption cooling system having a cooling capacity of 3.52 kW and was investigated experimentally under the climatic conditions of Taxila, Pakistan. Initially, a mathematical model was developed for LiBr/H₂O vapor absorption system alongside flat-plate solar thermal collectors to achieve the required operating temperature range of 75°C. Following this, a parametric analysis of the whole system was performed, including various design and climate parameters, such as the working temperatures of the generator, evaporator, condenser, absorber, mass flow rate, and coefficient of performance (COP) of the system. An experimental setup was coupled with solar collectors and instruments to get hot water using solar energy and measurements of main parameters for real-time performance assessment. From the results obtained, it was revealed that the maximum average COP of the system achieved was 0.70, and the maximum outlet temperature from solar thermal collectors was 75°C. A sensitivity analysis was performed to validate the potential of the absorption machine in the seasonal cooling demand. An economic valuation was accomplished based on the current cost of conventional cooling systems. It was established that the solar cooling system is economical only when shared with domestic water heating.     

Vary-therm wall for cooling/heating of buildings in composite climate

A modified form of Trombe Wall in which the glazing has been replaced by weather resistance material has been proposed and examined for winter heating and summer cooling in mixed climate conditions characterized by a mild winter and a relatively harsh dry summer. The experimental results indicate the potential applications of such a wall, known as Vary-Therm Wall, in solar passive building architecture for mixed climatic conditions.     

Performance of earth-air tunnel system for different earth surface treatments

Incorporating the effect of diurnal variations and annual variations of the environmental parameters (in a way similar to the analysis of amplitude modulation), the performance of an earth-air tunnel of infinite dimension along the horizontal direction has been analysed; dimensionless parameters have been used. The effect of earth storage on the performance of the tunnel has also been taken into account. The effect of modifying the earth's surface conditions, by wetting and shading, on the performance of earth-air tunnel system has also been investigated under two conditions: first when the inlet air is drawn from the ambient, and secondly when it is drawn from a conditioned room for recirculation to the room.     

Thermal management of hydrogen refuelling station housing on an annual level

A housing insulation of hydrogen refuelling station is vital from the aspect of safe operation of equipment in an environment that is installed. To secure hydrogen supply during the whole year, this work brings the solution for both cooling and heating insulation equipment inside of hydrogen refuelling station installed in Croatia, Europe. This hydrogen refuelling station was designed as an autonomous photovoltaic-hydrogen system. In the interest of improving its energy efficiency, an optimal thermal management strategy was proposed. To select the best technological solution for thermal management design which will maintain optimal temperature range inside the housing in cold and warm months, a detailed analysis of the system components thermodynamic parameters was performed. Optimal operating temperatures were established to be 25 °C in summer and 16 °C in winter, considering components working specifications. Insulation, type of cooling units, and heaters have been selected according to the HRN EN 12831 and VDI 2078 standards, while the regime of the heating and cooling system has been selected based on the station's indoor air temperature. The annual required heating and cooling energy were calculated according to HRN EN ISO 13790 standard, amounting to 1135.55 kW h and 1219.55 kW h, respectively. Annual energy share obtained from solar power plant used for the heating and cooling system resulted in 5%. The calculated thermal management system load turned out to be 1.437 kW.     

Thermal performance of a building coupled to an evaporative cooling tower

The thermal performance of a building fitted with an evaporative cooling tower has been evaluated in terms of discomfort index for two climates, namely, composite and hot-dry, typified by New Delhi and Jodhpur, respectively. The effects of various evaporative cooling parameters (height and cross-sectional area of the tower, packing factor, area of the pads, resistance offered to the air flow and local wind conditions) on the performance of the building have been analysed. It was found that, for given parameters of the tower and wind conditions, there is an optimum height of the tower for which the thermal discomfort condition in the building is minimum. The optimum values of the tower height for comfort conditions in the building for various other tower parameters have been obtained for each climate.     

太阳能吸收式空调及供热系统的设计和性能

一套太阳能吸收式空调及供热综合系统已在山东省乳山市建成。该系统由热管式真空管集热器、溴化锂吸收式制冷机、储水箱、循环、冷却塔、空调箱、辅助燃油锅炉和自动控制系统等内部分组成,具有夏季制冷、冬季供热和全年提供生活用热水等功能。太阳能集热器总采光面积540m∧2,制冷、供热功率100kW,空调、采暖建筑面积1000m∧2供生活用热水量32m∧3／d。文中着重介绍了系统的设计特点和测试性能。     

Life cycle cost analysis of HPVT air collector under different Indian climatic conditions

In this communication, a study is carried out to evaluate an annual thermal and exergy efficiency of a hybrid photovoltaic thermal (HPVT) air collector for different Indian climate conditions, of Srinagar, Mumbai, Jodhpur, New Delhi and Banglore. The study has been based on electrical, thermal and exergy output of the HPVT air collector. Further, the life cycle analysis in terms of cost/kWh has been carried out. The main focus of the study is to see the effect of interest rate, life of the HPVT air collector, subsidy, etc. on the cost/kWh HPVT air collector. A comparison is made keeping in view the energy matrices. The study reveals that (i) annual thermal and electrical efficiency decreases with increase in solar radiation and (ii) the cost/kWh is higher in case of exergy when compared with cost/kWh on the basis of thermal energy for all climate conditions. The cost/kWh for climate conditions of Jodhpur is most economical.     

An experimental study on multi‐purpose desiccant integrated vapor‐compression air‐conditioning system

In this paper, a multi‐purpose hybrid desiccant integrated vapor‐compression air‐conditioning system of a small capacity is experimentally investigated. The system, referred as hybrid desiccant‐assisted air conditioner (HDAC), is designed to meet the cooling load of spaces having large latent heat portions and at the same time to extract water from atmospheric air. The system is mainly consisted of a liquid‐desiccant dehumidification unit integrated with a vapor‐compression system (VCS). The dehumidification unit uses lithium chloride (LiCl) solution as the working material. The effect of different parameters, such as desiccant solution flow rate, process airflow rate, evaporator and condenser temperatures, strong solution concentration and regeneration temperature on the performance of the system, is studied. This system has a water recovery rate of 6.7 l/h TR (1.91 l/h kW) of pure water at typical north Egyptian climate (20–30°C dry bulb and 35–45% relative humidity). The HDAC system has a COP as high as 3.8 (an improvement of about 68% over the conventional VCS). The system offers a total cooling capacity of about 1.75 TR (6.15 kW) using a 0.75 TR (2.6 kW) VCS unit. Finally, the proposed system is found to have a payback time of about 10 months without any considerable extra capital cost compared with the known split air‐conditioning system. The results emphasize the potential benefits of the HDAC system. Copyright © 2010 John Wiley & Sons, Ltd.     

A study of the potential of using the Earth to air heat exchanger for cooling and heating of residential buildings in Iraq

The Earth to air heat exchanger (EAHE) is an effective passive cooling and heating system for buildings. This paper studied numerically the potential for reduction in energy consumption for cooling and heating loads for a residence equipped with an EAHE system in the climate of Nasiriya city, which is located in southern Iraq and at 31.7°N and 45.8°E, latitude and longitude, respectively. Also, this paper presents a study about the thermal performance of three types of EAHE systems, system 1, consisting of one layer of EAHE and buried at an available area of house garden with 3‐m depth, system 2, at the same site of system 1, but with two layers of EAHE at two depths, 3 and 4 m, and finally, system 3, buried along the area of the house at a depth of 3 m. First, the built numerical model was validated against experimental results, and the results of the comparison showed good agreement. The electricity consumption for cooling and heating of the house is calculated with and without the EAHE system. The results showed that with using EAHE, there is a considerable saving in energy and saving in the cost of electricity consumption, which reached 376 329 IQD ($301.11) over 1 year for system 2.     

Experimental investigation of two-phase closed thermosyphon used in heavy duty extrusion pelleting line

Efficient cooling system is an essential part of heavy duty extrusion pelleting line which plays an important role in production engineering of megaton polyolefin. In this paper, a new cooling system based on two-phase closed thermosyphon (TPCT) used in heavy duty extrusion pelleting line was presented. Comparative experimental results show that thermal performance of TPCT is more efficient, and the temperature uniformity is much better than traditional extruder (similar to coiled heat exchanger) in preheating process and extrusion reaction process. The effects of different operation conditions: filling ratio (0.2, 0.35, 0.5, 0.65 and 0.8), flow rate of cooling water (120 L/h, 180 L/h, 240 L/h, 300 L/h and 360 L/h) and heating power (7 kW, 9 kW and 11 kW) on thermal characteristics were experimental investigated, respectively. The results show that temperature of barrel inner wall increased significantly as filling ratio increased and evaporator appeared dry out when filling ratio is 0.2. The flow rate of cooling water affected the condenser section obviously, but had little influence on evaporation section. With increase of heating power, the start-up time decreases and the heat transfer coefficient increased. An ideal cooling scheme was concluded: the liquid filling ratio was 0.35, the cooling water flow rate was 180 L/h and the heating power was 11 kW when working medium was water.     

Energy metrics of photovoltaic/thermal and earth air heat exchanger integrated greenhouse for different climatic conditions of India

In this paper, a study is carried out to evaluate the annual thermal and exergy performance of a photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) system, integrated with a greenhouse, located at IIT Delhi, India, for different climatic conditions of Srinagar, Mumbai, Jodhpur, New Delhi and Bangalore. A comparison is made of various energy metrics, such as energy payback time (EPBT), electricity production factor (EPF) and life cycle conversion efficiency (LCCE) of the system by considering four weather conditions (a–d type) for five climatic zones. The embodied energy and annual energy outputs have been used for evaluation of the energy metrics. The annual overall thermal energy, annual electrical energy savings and annual exergy was found to be best for the climatic condition of Jodhpur at 29,156.8 kWh, 1185 kWh and 1366.4 kWh, respectively when compared with other weather stations covered in the study, due to higher solar intensity I and sunshine hours, and is lowest for Srinagar station. The results also showed that energy payback time for Jodhpur station is lowest at 16.7 years and highest for Srinagar station at 21.6 years. Electricity production factor (EPF) is highest for Jodhpur, i.e. 2.04 and Life cycle conversion efficiency (LCCE) is highest for Srinagar station. It is also observed that LCCE increases with increase in life cycle.     

Evaluation of discomfort in a room with desert cooler

The thermal performance of a room fitted with an evaporative cooler (desert cooler) has been analysed in terms of a ‘discomfort index’ for three different climates, namely hot dry, hot humid and composite typified by the Jodhpur, Madras and Delhi climates. The effects of different cooler parameters on the discomfort index of the room have been investigated to obtain the optimum values for each climate.     

燃气中央空调在上海及周边地区的市场分析(一)

燃气中央空调的市场发展前景主要和以下四个因素有关:当地的气候条件,社会需求量,电力和燃气的供应条件,技术经济性。首先就前面两个问题作专题分析。上海和江浙地区的自然气候使得一年中需要采暖的时间和需要空调的时间几乎相等,这可充分发挥燃气直燃型冷热水机组作为中央空调的优势;上海和江浙地区房地产业的迅速发展为中央集中空调系统的发展提供了广阔的市场,预计每年能形成6.0×105 kW的市场容量。