ASHRAE NY-08-035-2008 Recent Developments in the Design of a New Air-Cooled Hot-Water-Driven H2O-LiBr Absorption Chiller《新型风冷 热水带动H2O-LiBr吸收式制冷空调设计方案的最新应用》.pdf
《ASHRAE NY-08-035-2008 Recent Developments in the Design of a New Air-Cooled Hot-Water-Driven H2O-LiBr Absorption Chiller《新型风冷 热水带动H2O-LiBr吸收式制冷空调设计方案的最新应用》.pdf》由会员分享,可在线阅读,更多相关《ASHRAE NY-08-035-2008 Recent Developments in the Design of a New Air-Cooled Hot-Water-Driven H2O-LiBr Absorption Chiller《新型风冷 热水带动H2O-LiBr吸收式制冷空调设计方案的最新应用》.pdf(12页珍藏版)》请在麦多课文档分享上搜索。
1、288 2008 ASHRAE ABSTRACTThis paper explains the up-to-date stage of developmentof an air-cooled H2O-LiBr absorption chiller. The methodol-ogy of development is based on the systematic application ofadvanced numerical and experimental techniques, taking intoconsideration economical criteria. In a pre
2、vious developmentof a laboratory prototype of this concept of absorption chiller,two levels of mathematical modelling of different degree ofdetail, implemented for design/prediction purposes, wereexperimentally validated: (1) modelling of the absorptioncycle, based on overall balances of mass and en
3、ergy in thedifferent elements; (2) modelling of the heat exchangers of theabsorption cycle, that take into account the specific heat andmass transfer processes implied by means of semi-empiricalmodels. The same models have been applied for a new pre-industrial prototype.INTRODUCTIONIn the last decad
4、es a significant increase in electricityconsumption has been produced due to the growth in coolingdemand. In order to save energy in cooling systems it is neces-sary to develop new technologies to take advantage of alter-native energies, e.g. solar energy or waste heat.In the case of solar cooling i
5、nstallations, the main obstaclethat impedes an extended use of absorption systems is the largeinitial investment necessary for both solar collectors andabsorption machine. For low capacity installations (less than15 kW), the price of the chiller is the most limiting factor.Therefore, innovative desi
6、gns of both solar collectors andabsorption chillers (Ziegler 2002, Zogg and Westphalen 2006)to reduce prices are necessary. Moreover, a higher simplicityof the absorption cooling installation would reduce the cost ofthe investment significantly. Therefore, air-cooling for theabsorber and condenser c
7、an be an important issue to avoidusing a cooling tower. For solar air-conditioning applications,the refrigerant-absorbent pair H2O-LiBr is competitive withrespect the most universal pair NH3-H2O due to its higherperformance, but the use of LiBr as absorbent implies the riskof crystallization, more i
8、mportant in air-cooled systems.Different prototypes of air-cooled H2O-LiBr machines havebeen developed in the past decade for air-conditioning inbuildings (Ohuchi et al. 1994, Tongu et al. 1993, Enjoji 1998,Ishino and Kawasaki 1998, Kawakami et al. 1998). However,those machines were gas-fired. There
9、fore, the type of cycleused in those cases was double effect in order to get the maxi-mum advantage of the input energy. LiBr is sometimes used asabsorbent together with LiI to overcome the problem of crys-tallization (Tongu et al. 1993, Ishino and Kawasaki 1998). Themain problem for all those machi
10、nes relies on the high elec-trical consumption of the fans to create adequate cooling effecton the absorber and the condenser, because reduced andcompact designs were the main premises. Izquierdo et al.2001, presented an air-cooled absorber suitable for being usedin absorption systems for public tra
11、nsport, which took advan-tage of the engines waste heat.In the present research, an air-cooled absorptionmachine is being developed, in this case driven by hot waterbelow 100C (suitable for solar cooling applications) with asingle effect cycle configuration (Figure 1). Although thefinal performance
12、of the system is slightly reduced due to theair-cooling, in both the absorber and condenser the mainpremise of design has been to keep the electrical fan con-sumption in these elements within moderate limits. Themachine developed has a mechanic solution pump, whichRecent Developments in the Design o
13、f a New Air-Cooled, Hot-Water-Driven H2O-LiBr Absorption ChillerJess Castro, PhD Assensi Oliva, PhDCarlos David Prez-Segarra, PhD C. Oliet, PhDJess Castro, Assensi Oliva, Carlos David Prez-Segarra, and C. Oliet are mechanical engineers with the Centre Tecnolgic de Transfer-ncia de Calor (CTTC), Univ
14、ersitat Politcnica de Catalunya (UPC), Barcelona, Spain.NY-08-0352008, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 114, Part 1. For personal use only. Additional reproduction, distribution, or transmission
15、 in either print or digital form is not permitted without ASHRAEs prior written permission.ASHRAE Transactions 289leads to a different behavior of the machine compared to theheat powered pumps used in the commercially availablewater fired chillers. These chillers experiment a drasticdecrease of the
16、COP due to the decrease of the circulatedmass flow at low driving temperatures (Yazaki 1996). Themachine developed consists in horizontal tube, falling filmgenerator and evaporator, and air-cooled absorber and con-denser that are tube-fin heat exchangers (see Figure 1) wherethe falling film absorpti
17、on and condensation processes is pro-duced in the interior of the tubes.The main novelty from the point of view of final productis the implementation of an air-cooled absorber and condenserin a hot water driven H2O-LiBr machine. From the point ofview of the methodology, the main novelty is the syste
18、maticapplication of mathematical models for the design and predic-tion of the thermal behavior of the new prototype. With thisstrategy of simulation, it will be possible to make an accuratedesign of the cycle and heat exchangers, avoiding situationswith risk of crystallization from the thermal desig
19、n and spec-ifying accurately the suitable conditions of operation. Theselimited operating conditions have been implemented bymeans of a control strategy. This methodology saves develop-ment costs by means of reduction of experiments.RESEARCH APPROACH AND METHODOLOGYThis research will complete the in
20、dustrialization of theabsorption cooling machine that was the result of the Euro-pean funded project CRAFT ACABMA (Oliva et al. 2002),with the following final objectives:1. Introduction into the market of a new air-cooled absorp-tion chiller of low capacity using H2O-LiBr as fluid pair.This machine
21、should have a final price lower than theones existent in the market, all of them water-cooled, thatneed cooling tower.2. To dispose of the necessary infrastructures (demonstra-tion plants) that assure the maximum diffusion of the newabsorption chiller, facilitating its introduction to themarket.Meth
22、odology of AnalysisThe methodology adopted in the development of theabsorption chiller is general for any thermal system:Exhaustive analysis of the physical phenomena andgeometry. This work was already performed in the firststage of the ACABMA project, first laboratory prototype.Proposal of possible
23、 mathematical formulations. Studyof the diverse possibilities of use of levels of modelisa-tion of different degree of detail.Numerical resolution of the governing equations. In thispoint all the numerical solutions must be checked in orderto achieve results with no programming errors and notdepende
24、nt of the calculation mesh used (verification ofnumerical errors).Experimental validation. Comparison of the numericalpredictions with the results obtained in an experimentalfacility, in this case the laboratory prototype developed inwithin the European project.Figure 1 Single-effect, air-cooled abs
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