A simulation appraisal of performance of different HVAC systems in an office building

The article reports on a simulation appraisal of energy consumption, energy costs and environment impact of three systems used for space heating, and space cooling of an office building in Kragujevac, Serbia. Three investigated systems are (1) a system with a natural gas boiler and convective baseboard heaters for water space heating and window air conditioners for air space cooling; (2) a system with a natural gas boiler and individual air reheaters for air space heating and a chiller plant for air space cooling; and (3) an air-to-air heat pump for air space heating, and cooling. The systems are modeled and simulated by using EnergyPlus software. After simulations, it is found that the first investigated system has the highest energy efficiency, the best economy, and the lowest environmental impact. That is because of the fact that the first system has water as a heating medium and uses predominantly natural gas as fuel. However, in future, when for generation the grid electrical energy requires less primary energy, and becomes decarbonized, the third system would be best to conserve energy resources and environment.     

热源塔在江苏某培训大楼的应用

本文介绍了江苏某培训大楼的暖通设计,培训大楼采用了热源塔作为冷热源。介绍了热源塔系统的工作原理,分析了3个月的实际运行数据,指出在常州地区热源塔系统的冬季能耗效率和锅炉系统接近,但是费用相比并不节省。     

TRNSYS simulation for solar-assisted liquid desiccant evaporative cooling

ABSTRACT

Recently, desiccant cooling systems are well thought of as a competent method for controlling the water content in the air. A solar flat-plate collector has been used as it decreases the dependency on non-renewable resources. Solar-aided liquid desiccant systems have been used to reduce the dependency of air-conditioning systems on non-renewable sources of energy. Manipal’s humid and searing climate provides certain benefits in setting up such a system. The suggested system has reliability and equipment life and also takes complete advantage of the available solar energy for the renewal of the liquid desiccant. TRNSYS simulation is used to predict the efficiency and feasibility of the system. The temperature and energy-load variations were successfully obtained. An effective simulation was developed whereby the solar air conditioning of a room was indicated.     

Experimental study on dehumidifier and regenerator of liquid desiccant cooling air conditioning system

A new type of air conditioning system, the liquid desiccant evaporation cooling air conditioning system (LDCS) is introduced in this paper. Desiccant evaporation cooling technology is environmental friendly and can be used to condition the indoor environment of buildings. Unlike conventional air conditioning systems, the system can be driven by low-grade heat sources such as solar energy and industrial waste heat with temperatures between 60 and 80 °C. In this paper, a LDCS, as well as a packed tower for the regenerator and dehumidifier is described. The effects of heating source temperature, air temperature and humidity, desiccant solution temperature and desiccant solution concentration on the rates of dehumidification and regeneration are discussed. Based on the experimental results, mass transfer coefficients of the regeneration process were experimentally obtained. The results showed that the mean mass transfer coefficient of the packing regenerator was 4 g/(m² s). In the experiments of dehumidification, it was found that there was maximal tower efficiency with the suitable inlet humidity of the indoor air. The effective curves of heating temperature on the outlet parameters of the regenerator were obtained. The relationships of regeneration mass transfer coefficient as a function of heating temperature and desiccant concentration are introduced.     

数据中心冷却塔供冷应用分析

针对数据中心能耗问题,分析了冷却塔供冷的关键因素,如热工曲线、湿球温度、工况切换点等,指出冷却塔厂家应提供冬季供冷工况下热工曲线等信息,冷却塔供冷按冬季工况选取,夏季校核,结合夏季工况灵活配置,指出冬季供冷以小于冷却塔的额定流量来获取较低出水温度延长冷却塔供冷时间,冷却水泵应设变频,适应管网特性曲线变化等设计方法,为数据中心节能设计提供参考与依据。     

冷却塔风机运行节能之模式与策略的分析

冷却塔风机是整个冷却水系统的核心设备,其运行状况直接关系到系统性能与能耗状况.本文针对国内某办公建筑的冷却塔风机运行状况进行实测,从风机与变频器电耗、冷却塔效率、冷机COP,设备寿命与运行策略的可行性4个方面分析评价了风机运行模式和策略对能耗的影响.     

Effects of alternative control strategies of water-evaporative cooling systems on energy efficiency and plume control: A case study

This paper reports the evaluations of energy efficiency, plume potential as well as plume control of a huge chiller plant using water-evaporative cooling towers for heat rejection for a super high-rising commercial office building in a subtropical region of Hong Kong. The evaluations were carried out in a dynamic Transient Simulation Program (TRNSYS)-based simulation platform using alternative control strategies including set-point control logics of the supply cooling water temperature and cooling tower fan modulation control methods as well as different number control means of cooling towers. The results show that different control strategies have significant effects on the energy efficiency of the chiller plant. The quantification of the energy efficiency demonstrates significant energy-saving potential by using advanced technologies for implementing optimal control strategies in this cooling system. The results also reveal that the plume may occur frequently in spring and summer seasons and occasionally in other months due to the odd subtropical weather conditions. Control strategies also have significant effects on the frequency of the plume occurrence. The effective energy efficiency control and effective plume control using wet–dry (i.e., hybrid) cooling towers are also discussed.     

居民用户天然气供暖方案

以包头市北部新区居民用户的天然气供暖方案为例,对比分析了燃气壁挂炉供暖、燃气壁挂炉与太阳能联合供暖、模块式燃气锅炉楼栋供暖、燃气区域锅炉房供暖、燃气热泵空调供暖、燃气冷热电三联供、天然气红外线辐射供暖7种供暖方案的技术特点,对比较适合居民用户供暖的前4种方案进行了工程建设造价和运行费用对比分析。燃气壁挂炉供暖方案工程造价最低,运行费用较少,节能效果较好;燃气壁挂炉与太阳能联合供暖方案工程造价最高,但其运行费用最少,节能效果最佳。     

Application of solar energy for milk pasteurisation: a comprehensive review for sustainable development

ABSTRACT

Solar energy is available freely. Hence, nowadays people are working on solar energy when compared with conventional sources of energy. Dairy industries require heat, which can be generated by the use of boiler with the aid of wood. Hence, due to increment in global warming, it is necessary to use renewable energy. The primary aim of this review paper is to study various researchers’ work on solar milk pasteurisation system. Hence, it also covers important aspects required for solar pasteurisation like flat plate collector, heat exchanger and solar water heating system.     

Effective design and operation of hybrid ground-source heat pumps: Three case studies

One innovation to ground-source heat pump (GSHP, or “geothermal”) systems is the hybrid GSHP (HyGSHP) system. A HyGSHP system can dramatically decrease the first cost of GSHP systems by using conventional technology (such as a cooling tower or a boiler) to meet a portion of the peak heating or cooling load. We monitored and analyzed three buildings employing HyGSHP systems (two cooling-dominated, one heating-dominated) to demonstrate the performance of the hybrid approach. The buildings were monitored for a year and the measured data was used to validate models of each system. Additionally, we used the models to analyze further improvements to the hybrid approach and established that it has positive impacts, both economically and environmentally. We also documented the lessons learned by those who design and operate the three systems, including discussions of equipment sizing, pump operation, and cooling tower control. Finally, we described the measured data sets and models from this work and have made them freely available for further study of hybrid systems.     

Application of radiant cooling as a passive cooling option in hot humid climate

In hot and humid region, air-conditioning is increasingly used to attain thermal comfort. Air-conditioning is highly energy intensive and it is desirable to develop alternative low-energy means to achieve comfort. In a previous experimental investigation using a room equipped with radiant cooling panel, it was found that cooling water kept to 25 °C could be used to attain thermal comfort under some situations, while water at such temperature would not cause condensation of moisture from air on the panel. This paper reports results of a series of whole-year simulations using TRNSYS computer code on applications of radiant cooling to a room model that represents the actual experimental room. Admitting the inability of radiant cooling to accept latent load, chilled water at 10 °C was supplied to cooling coil to precool ventilation air while water cooled by cooling tower was used for radiant cooling in daytime application. For night-time, cooling water from cooling tower supplied for radiant cooling was found to be sufficient to achieve thermal comfort. Such applications are considered to be more amenable to residential houses.     

Energy consumption criteria and labeling program of wet cooling towers in Iran

Increasing concerns about the lack of energy resources, global warming and environmental pollution have pushed the relevant organizations to develop energy saving strategies such as energy labeling programs. In this research, a new energy labeling program is developed and evaluated for the wet cooling towers in Iran. The cooling tower parameters, including its cooling capacity and the fan power consumption, are measured using an experimental setup. The experimental data are standardized to compensate the effect of the ambient wet bulb temperature on the cooling tower performance which cannot be controlled during the experiments. The results show that the cooling tower capacity and the fan power consumption may be correlated properly using a linear function which conducts the authors to present a linear energy index (EI). Based on the statistical analysis of a comprehensive range of products, the energy rating limits are extracted for the main types of cooling towers, including induced draft and forced draft ones. The economical and environmental impression of the program authorization is also discussed in detail. Administration of such program may lead to considerable energy saving in the cooling systems which have major economical and environmental benefits, especially in the large industries.     

Low exergy systems for high-performance buildings and communities

There is an obvious and indisputable need for an increase in the efficiency of energy utilisation in buildings and in the energy supply system within communities. Heating, cooling and lighting appliances in buildings account for more than one third of the world's primary energy demand. In turn, building stock is a major contributor to energy-related environmental problems and CO₂ emissions. There are great potentials to be obtained through a more efficient supply of energy and rational use of energy in buildings.An optimisation of the exergy flows in buildings and related supply structures, similar to other thermodynamic systems such as power stations, can help in identifying the potential of increasing efficiency in energy utilisation. Through analyses, it can be shown that calculations based on the energy conservation and primary energy concept alone are inadequate for gaining a full understanding of all important aspects of energy utilisation processes. The high potential for a further increase in the efficiency of; for example, boilers, cannot be quantified exclusively by performing energy analyses—the energy efficiency is close to 100%; however, this potential can be demonstrated by using an exergy analysis, whereby the exergy efficiency of a common gas boiler is about 8%. It is necessary to work out new and more efficient ways to supply energy to satisfy the demand for energy services.This paper outlines the international co-operative work in the general framework of the International Energy Agency (IEA), the ECBCS Annex 49 “Low Exergy Systems for High Performance Buildings and Communities” [Annex 49, Energy Conservation in Buildings and Community Systems—Low Exergy Systems for High Performance Buildings and Communities, homepage: http://www.annex49.com, 2007].     

An ETTV-based approach to improving the energy performance of commercial buildings

This paper aims to study the various parameters that affect the energy performance of commercial buildings in Singapore. The parameters are diverse, ranging from characteristics of construction of the walls and windows, to the various system settings and types within the building. Building energy performance is measured via two key indexes, namely, the Envelope Thermal Transfer Value (ETTV) and the annual cooling energy requirement (E_c). Parameters related to these two indexes are identified. An additional parameter, the solar absorptance of the wall, is further incorporated to calibrate the ETTV equation. A relative ranking on the functional parameters of ETTV has been performed to evaluate their effectiveness in lowering the ETTV of buildings. In addition, the impact of using cladding on ETTV is also studied. A correlation for E_c, expressed in the form of a simple linear equation, has been developed. This correlation accounts for the internal building loads, envelope loads, operating schedules and efficiency of the cooling equipment. Finally, ETTV and E_c have been employed to study the effects of chiller over-sizing and ventilation rates on building cooling energy. In the pursuit for better energy-efficient buildings, the approach presented in this paper contributes to the construct of sustainable energy-efficient built-environment.     

Operation costs exergoeconomic of transcritical refrigeration cycle with carbon dioxide

ABSTRACT

In this work, the thermodynamic and exergoeconomic studies are performed to a single vapour compression refrigeration cycle which uses CO₂ as a refrigerant in transcritical conditions. This analysis establishes the behaviour of the compressor discharge pressure based on the gas cooler temperature, when it is operating at ambient conditions greater than 20°C. The effect of varying the cooling chamber temperature is also shown. In the analysis, the coefficient of performance (COP), exergetic efficiency and exergoeconomic operation costs for each equipment are obtained, considering a refrigeration capacity of 5 TR. For instance, at a gas cooler temperature of 45°C and a cooling chamber temperature of ?5°C, the maximum COP is 1.78 to a gas cooler pressure of 120 bar and the exergetic efficiency is 0.1556; however, operating at these conditions, it generates an exergoeconomic operation cost of 1.74?€?h^?1.     

Effects of utilizing seawater as a cooling source system in a commercial complex

This paper treats energy and cost performance of a cooling source system with indirect seawater utilization for air conditioning in a commercial complex. Seawater utilization has merits as a cooling source, because seawater temperature is lower than outdoor air in summer and it is cost effective because there is no water monetary cost. Actual operating data has been measured for about 2 years and the chiller and system co-efficient of performance (COP) have indicated about 4.77 and 2.93, respectively, even in summer season and the mean efficiency of the thermal storage system was about 89.9% taking into account heat loss of pumps. In addition, we have constructed simulation models for cooling tower systems, air cooling chiller systems and direct seawater utilization systems then compared them to this system. The electric power consumption of the indirect seawater utilization system was almost the same as the other systems except the air cooling chiller system, because using lower seawater temperature made the chiller efficiency higher. In conclusion, our results showed the indirect seawater utilization system was able to improve the system COP compared to air cooling chiller system, and cancel water consumption compared with the cooling tower system, and cut down an initial and maintenance costs compared with the direct seawater utilization system.     

生物氧化塔/过滤/RO工艺处理二级出水并回用

大连北海热电厂以某污水厂二级处理出水为水源,采用生物氧化塔/纤维束和砂滤二级过滤/RO组合工艺,建设了污水深度处理与回用工程(主要用作循环冷却水和锅炉补水处理系统的原水).运行结果表明,采用单膜法进行污水深度处理是可行的,具有处理效果好、运行稳定、工程投资省、运行费用低等优点.     

贵阳市原生污水源热泵空调系统运行实测及分析--贵州省某办公大楼污水源热泵系统

城市原生污水源热泵系统,具有低能耗、环保等特点。本文以贵州某办公大楼项目空调系统为污水源热泵系统为主系统,燃气锅炉、冷却塔系统为备用系统。结合工程的实际使用情况,对使用中存在的问题进行了实测及分析。     

空调系统冷却水温度分析

在常用冷却塔计算方法的基础上,建立了适合空调用冷却塔出水温度的计算方法,并编写计算程序对不同状态下的空调用冷却水温度进行了计算,计算结果可以作为空调机组效率分析的基础。     

冬季冷却塔供冷系统在长沙卷烟厂的节能应用

本文通过对长沙卷烟厂生产车间冬季和过渡季节的供冷需求和长沙室外气象条件的分析,提出在冬季和过渡季节,采用冷却塔对产热量较大的卷烟生产车间进行供冷,可实现冷冻站节能运行的目的。本文结合长沙卷烟厂的运行实践,对冬季或过渡季节冷却塔供冷的系统设计、热工性能、全年运行时间、节能效果以及投资回收期进行了计算和分析。