Optimization of Selecting Air Conditioning Cold/Heat Sources with Grey Relation Analysis

Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categorize the correlation extent of compared sequences and a certain reference sequence in a system with uncertain information. It is applied to evaluating and selecting AC cold/heat sources from four main aspects, which are technology, economy, reliability, and operation and management. Case study shows that the result for selecting AC cold/heat sources with the GRA method can be more reasonable and convincible. Thus it offers a new approach for designers in heating, ventilating and air conditioning field to compare and evaluate different AC cold/heat sou rces.

Energy Efficient Air Conditioning System Using Geothermal Cooling-Solar Heating in Gujarat, India

It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.

Field experimental study on the cooling effect of mine cooling system acquiring cold source from return air

With the increase of mining depth, more and deeper coal mines are limited by heat disaster. The cooling energy in deep mine cooling system comes from mine water inrush or ground cooling tower, but we cannot adopt the two methods because mine water inrush in many old coal mines in China is limited. What is more, the cooling pipelines cannot be put in narrow pit-shaft. To settle the problem above, according to the characteristics of Zhangxiaolou Coal Mine, this paper adopts the deep mine return air as the cooling energy for deep mine cooling system. In addition, we carried out cite test to extract cold energy from return air. Through monitoring the water quantity, water temperature of cooling system and air temperature, we got the thermodynamic equilibrium parameters during the cooling energy acquisition analysis and the effect of cooling system that the temperature and humidity on working face are respectively reduced to 8-12 ℃ and 8-15% through cooling. This research offers experimental reference for deep mine cooling which lacks cooling energy.

Characteristic studies of heat sources and performance analysis of free-cooling assisted air conditioning and ventilation systems for working faces of mineral mines

High temperature heat hazard at mineral mine becomes more and more serious as the increase of mining depth.Heat sources at working faces of mineral mines are complex and are of different characteristics,presenting new challenges for air conditioning systems.In this paper,heat sources at four types of working faces are summarized and their characteristics are investigated.Based on this,simplified equations,which are linear with length of working faces,are proposed to calculate heat dissipation rates.So that the main heat sources of different working faces can be found,and cooling load of air conditioning systems can be calculated.Then,considering main heat sources of coal mines,a typical working face is designed to investigate performances of different ventilation systems and air conditioning systems.Simulation results show that segmented ventilation systems(SC)and heat shield assisted centralized ventilation systems(CCHS)can realize much better temperature distributions at working faces.However,cooling load can be greatly reduced for CCHS,when untreated air is supplied to the coal seam side.Based on this,free cooling assisted air conditioning systems are designed,and annual average energy efficiency ratio(EERann)of the systems are investigated and compared between direct evaporate cooling and indirect evaporate cooling(IEC).For SC,as compared with scenarios without free-cooling,IEC can increase EERann by 15%-23%and 22%-32%under Benxi and Datong ambient conditions,respectively.Besides,to ensure high EERann,CCHS is preferred and it is essential to increase thermal insulation of air ducts.

Analysis of the Thermal Performance on Cooling and Dehumidifying Process in Air Washer

On the bads of theory and experiment, this paper studies and analyses the factors such as water - air ratio, air velocity, spraying water pressure and initial water temperature, which affect the heat and mass transfer in air washer , thus can help us to reduce the power consumption and Improve the efficiency of heat and mass transfer.

Investigation on the Influence of Refrigerant Charge Amount on the Cooling Performance of Air Conditioning Heat Pump System for Electric Vehicles

The application of air conditioning heat pump(ACHP) in electric vehicles could lead to significant electrical power saving effect. As for an air conditioning heat pump system for electric vehicles, the influence of refrigerant charge amount should be investigated during the design phase. In this study, experimental method was employed to investigate the influence of the refrigerant charge amount on the performance of the ACHP system. The results showed that the refrigerant charge amount had different influence on the refrigerant properties at various locations within the system. The coefficient of performance and pressure-enthalpy diagram were calculated, and showed a close relationship with refrigerant charge amount under different compressor speeds. The degree of subcooling and the degree of superheating were recorded and the critical charge amount was determined by a typical practical test method. In addition, the critical refrigerant charge amount determined by the experimental method was also compared with two typical void fraction correlation models, and the model with consideration of two phase stream reaction of the refrigerant showed a good estimation accuracy on the critical charge amount.

A concept of capillary active,dynamic insulation integrated with heating,cooling and ventilation,air conditioning system

When a historic façade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation,one needs to use interior thermal insulation systems.Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges.Yet they may be successfully used and,in many instances,are recommended as a complement to the exterior insulation.This paper presents one of these cases.It is focused on the most successful applications of capillary active,dynamic interior thermal insulation.This happens when such insulation is integrated with heating,cooling and ventilation,air conditioning(HVAC)system.Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations,we propose a next generation,namely,a bio-fiber thermal insulation.When completing the review,this paper proposes a concept of a joint research project to be undertaken by partners from the US(where improvement of indoor climate in exposed coastal areas is needed),China(indoor climate in non-air conditioned concrete buildings is an issue),and Germany(where the bio-fiber technology has been developed).

Application of the ground cooling system for rural houses air conditioning in northeastern China

This study developed an appropriate ground cooling system that can be used for indoor cooling during summers in rural houses in northeastern China.To apply this system,a traditional rural house was selected and a heat exchanger was designed(PE pipe,32 m in length),manufactured,and installed according to the cooling load(2206 kJ/h)of one room of the experimental house.According to the experiment,the temperature of Room 1 equipped with the cooling system was 3℃ lower than that of Room 2 without the ground cooling system during the same time period.The temperature reduction effect of this system was confirmed through this study.When the ground cooling system was used in rural houses in Northeast China,it was found that a burial depth of 1.5-2.0 m for the ground heat exchanger is appropriate for considering workability and frost line.The use of the ground cooling system for indoor cooling during summers for rural houses in the northeastern region of China would reduce not only environmental pollution and the use of fossil fuels but also ease farmers off a certain amount of financial burden.

融霜工况影响下空气源热泵机组频率控制系统

空气源热泵机组在融霜工况下,由于外部环境温度低,机组内部的水箱和管路可能会结霜,导致传热效率下降、能耗增加,使得频率控制不精准。为此,设计融霜工况影响下空气源热泵机组频率控制系统。设计PLC频率控制结构、频率控制中央处理器与PID控制阀门,联合控制热源侧水泵变频。计算机组结霜量,获取换热器的有效集热量。基于分段调节思想,利用计算机调整侧水泵出水量和调节参数,计算融霜启动调频速度。由实验结果可知,所设计系统在不同融霜工况下控制效果与实际最为接近,控制结果误差最大仅为0.1 Hz,能够实现精准控制频率。

地埋管换热系统改造项目关键技术节点施工工艺研究

天津某管业公司建筑原采用常压燃气热水锅炉供热和分体式空调供冷,现拟以浅层地热能为基础能源对原供热制冷系统进行改造,施工前首先通过现场岩土热响应试验、地下管线探测等查明施工场地岩土体结构和换热能力,掌握地下综合管线的分布,并对建筑单位冷热负荷指标校正。重点阐述地埋管换热系统施工过程的关键技术节点,即竖直换热孔钻进、下管、回填及水平管线连接等,为类似改造项目提供参考。

基于决策树算法的冷冻水系统优化运行研究

以四川省成都市某办公建筑空气源热泵中央空调系统为研究对象,针对冷冻水系统制定夏季供冷工况下变冷冻水供水温度与变冷冻水流量相耦合的优化运行策略。首先依据运行数据确定出建筑负荷的主要影响因素;其次结合影响因素依据建筑负荷建立决策树算法,将系统运行工况分为7类;最后整理出每种分类工况下空调系统能效COPsys的分布情况,并以COPsys最高时对应的冷冻水供水温度和冷冻水泵设定频率作为该工况下最佳设定参数。结果表明:以上一年度的运行条件为基准,使用该运行策略在保证室内环境舒适度要求的前提下,夏季可以节约33%左右的电量,有效提升了中央空调系统的运行效率。

环境风影响下换流变压器空冷换热系统换热能力衰减特性研究

为实现换流变压器冷却系统换热容量的合理设计并保障其安全稳定运行,研究了环境风影响下换流变压器空冷换热系统换热能力的衰减特性。针对北方某换流站换流变压器,采用基于空冷换热系统大尺度热量传递与换热器翅片管束小尺度换热计算相耦合的方法,建立了包含空冷换热器、风机、防火墙、环境风等多种因素在内的三维传热流动数值分析模型。研究了环境风向及风速对空冷换热系统换热能力的负面影响机制,获得了真实环境条件下换热能力的衰减特性。结果表明:正前方风向下,换热器进风体积流量随风速增加而显著减小、进气温度略有下降,导致不同风速下换热效率维持在66.01%~66.75%之间;侧方风向下,迎风侧防火墙阻碍了气流运动,导致换热效率随风速增加在55.98%~83.13%之间变化,其中环境风速为6 m/s时换热效率最低;正后方风向下,与风机出流方向相同的环境风引起换热器附近更加剧烈的热风回流,导致换热效率随风速增加,在50.96%~91.46%之间变化,其中环境风速9 m/s时换热效率最低。研究结果可为换流变压器空冷换热系统换热容量的设计提供一定的参考。

北京某大型商场空调系统节能改造方案分析

大型商场人流量大、散热设备多、空调系统运行时间长,有较大节能潜力。调研了北京某大型商场空调系统的能耗情况,针对其运行过程存在的问题,提出了一套基于空调系统节能控制技术的综合节能改造方案。研究表明,该空调系统节能改造后,年节电量为140.56万k Wh,每年节省电费160.24万元;节热量为601.82GJ,每年节省供热费用5.95万元,节能效果与经济效益较好,可为北京地区类似公建节能改造提供借鉴和参考。

夏热冬冷地区空调冷热源配置的多目标优化

为实现“双碳”背景下清零建筑直接碳排放的目标,夏热冬冷地区建筑空调冷热源越来越多地采用空气源热泵加水冷式冷水机组的复合架构。其中,空气源热泵冬季供热,夏季与水冷式机组共同供冷。由于空气源热泵供冷能效较低,提高水冷式机组容量配置,尽可能使之分担更多的冷负荷,有利于降低系统供冷能耗,但系统投资也将随之上升。因此,有必要研究复合架构下空调冷热源配置的综合优化方法。利用层次分析法,计算空调冷热源系统的节能性、环保性、经济性、节材性等不同目标维度的权重,建立空调冷热源的综合优化目标函数。设计空调冷热源配置的优化流程,并以上海某办公建筑为例进行分析。结果表明,随着水冷机组容量的增加,空调冷热源系统的全年能耗降低,耗材生产能耗、折算年费上升,而碳排放呈先降后升的规律。多目标优化方法可以更好地实现各项指标之间的平衡,为相关研究及实际项目决策提供参考。

喷油参数对螺杆式空气源热泵系统性能的影响

针对北方寒冷地区的稠油热水驱技术面对的问题,设计一台带经济器的螺杆式低温空气源热泵加热原油机组,增加油冷热回收系统,测试分析低温环境下热泵系统的制热性能以及油冷热回收对系统性能的影响。结果表明:油冷换热器可以有效帮助螺杆式空气源热泵降低压缩机排气温度,提高热泵在低温环境下的制热量和能效比C_(op),实现环境温度-35—43℃的稳定运行。有油冷热回收时,系统能效比最高可达3.74,油冷换热器最高能回收25.8%的热量。蒸发温度-24℃时,制热量可达350 kW。喷油量的增加对系统性能的改善呈现先增加后下降的趋势,油冷热回收回路存在最佳喷油量使得系统能效比最高。随着喷油温度的增加,压缩机排气温度呈上升趋势,系统能效比呈下降趋势。

太阳能—地源热泵式空调自适应模糊PID复合控制方法

为了优化太阳能-地源热泵空调系统的能耗和效率,减少环境因素对稳定运行的影响,提出自适应模糊PID复合控制方法。通过监控管理层上位机采集现场数据信号,并下发开关量信号至PLC控制器,再通过PLC控制器对太阳能集热器、循环水泵和温度进行控制。同时,将模糊PID控制器作为子程序控制循环水泵的频率,温度误差和误差变化率作为复合控制器的输入,通过模糊化处理输入信号,调节PID控制的相关参数,输出控制变频器频率的信号,以调节水泵电机的运转速度,精准控制室内温度。实验结果表明,该方法能提高太阳能的利用率,具有较好的抗干扰性能和较高的制冷、供暖性能系数,可实现高效的节能效果。

基于AHP-CRITIC的集中空调冷热源系统用能画像分析

近年来,随着集中空调系统的应用日益普及,空调能耗呈增长趋势。空调能耗在建筑运行能耗中占据较大的比重,一个合理的集中空调系统能够有效地降低建筑对能源的需求。为此,本文构建了集中空调冷热源系统用能特性评价指标体系。从冷/热能利用、电能利用、系统能效及碳排放特性4个方面构建了相应的评价指标,建立了包括目标层、准则层和指标层的指标综合评价体系。利用层次分析法(AHP)与客观权重赋权法(CRITIC)确定了指标权重并计算了综合用能特性分值,建立了集中空调冷热源系统用能画像。以某办公楼集中空调冷热源系统为例,得到了其夏季工况和冬季工况的用能画像结果,验证了所提方法的有效性。

上海市某超高层办公楼空调系统调适

通过详细检测上海市某超高层高档办公楼项目的空调供热系统和制冷系统的运行状况,确认了锅炉、冷水机组和相应水泵等设备运行使用中存在的问题。开展了空调系统调适,在不进行设备改造的情况下,通过整改设备运行问题和调整自控程序,解决了大楼冬季空调供热功能失灵的问题,并提高了制冷系统的节能性。根据新建和既有公共建筑机电系统调适项目的经验,提出几点建议,为其他项目空调系统的运行调适提供参考。

双碳背景下基于某项目的地下水冷热源方案探讨

结合某工程项目附近有大量地下矿坑水的实际情况,比较分析中央空调水系统(冷水机组+热水锅炉)、地下水源热泵空调系统、水源多联机空调系统及空气源多联机空调系统这4种常见空调形式在本项目中的适用性与可行性。借助设计分析软件对项目建筑进行负荷计算、机房提效寻优、建模并模拟制冷运行工况,基于供暖运行负荷及运行时间计算冬季系统运行费用;通过动态年值和运行阶段碳排放分析,结果表明:在有低品位能源可利用的前提下,水源多联机空调系统方案的经济性和碳排放强度具有明显优势。

武汉某国际商务区暖通空调冷热源工程设计

武汉某国际商务区江水源能源站项目被评为湖北省2019年建筑节能示范工程,本文对该项目的暖通空调冷热源工程设计进行了介绍,阐述了采用可再生能源——江水为冷、热源、利用热泵技术为商务区提供空调用冷、热水的方案,介绍了冬季供冷的四管制设计思路,同时对空调水系统进行了设计,阐述了采用二次泵+一次泵变流量设计的合理性等;设计内容可为大规模商务区集中供冷供热的暖通空调冷热源系统设计提供参考。