摘要:

AbstractA computational model of the transient thermal response of a packed bed of spheres containing a phase‐change material (PCM) is presented. A one‐dimensional separate phases formulation is used to develop a numerical analysis of the dynamic response of the bed which is subject to the flow of a heat transfer fluid, for arbitrary initial conditions and inlet fluid temperature temporal variations. Phase‐change models are developed for both isothermal and nonisothermal melting behaviours. Axial thermal dispersion effects are modelled, including intraparticle conduction (Biot number) effects. Regenerative thermal storage applications involve flow reversals to recover the stored energy; this aspect of operation is included in the present model.Results from the model for a commercial sized thermal storage bed for both the energy storage and recovery periods are presented. Experimental measurements of transient temperature distributions in a randomly packed bed of uniform spheres containing a PCM for a step‐change in inlet air temperature are reported for a range of Reynolds

ISSN:0363-907X    

DOI:10.1002/er.4440130302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractElectrical energy consumption and the peak electrical demand were measured at two similar public housing sites in Selma, North Carolina. One site, designated as Preston Street (PST), had low cost energy retrofit measures combined with education of the occupants on energy efficient life styles. The other site, Canady Courts (CC), was originally planned as a control site. Both sites are single‐storey wood‐frame with brick‐veneer construction. The sites consisted of a combination of efficiency and 1,2,3, and 4‐bedroom units. PST consisted of 30 units with a total floor area of 22,000 ft2and CC had 26 units with a total floor area of 18,800 ft2. Originally CC was intended to be used to quantify the impact of the energy conservation project undertaken at PST. This approach proved inadequate, and consequently an alternate methodology was employed. This method used the measured historical energy at both CC and PST to develop a database that could be used to predict the energy use that would be expected to occur at either site. If there are no changes at the site, then the predicted and measured energy use should agree. When conservation measures are instituted, the difference between predicted and measured energy use is the energy saving (or increase) due to the conservation measures. The report gives a description of the methodology that was used to analyse the historical data and the results and accuracy that were obtained. In addition, the problems with using one site as a control, as originally planned, are described. The Section on results gives a comparison of the predicted and measured energy use at both CC and PST for the calendar year 1985. The last part of the report deals with the investigation of the demand profiles and demand at PST. This analysis indicates the nature of the demand profiles at PST and thus the types of conservation measures that are likely to be the most effective in reducing

ISSN:0363-907X    

DOI:10.1002/er.4440130303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractBoth producers and consumers of electric energy have challenging decisions to make. In some cases, these decisions are related to the selection of specific equipment for energy production or energy conversion. The important financial and operational decisions that face these companies merit the use of an analytic approach to decision making. Of special interest is the purchase of high volume equipment used in the daily operation of energy production or conversion.This paper presents a method that utilizes all available information when making a decision, regardless of the size of the problem. The method is based on the analytical hierarchy process (Saaty, 1980). An example is shown demonstrating the selection of one of the most common energy conversion devices, namely a distribution transformer. Distribution transformers are rank ordered according to manufacturers using this decision support technique. Finally, a user friendly software package implementing this method is fully developed on a personal computer.

ISSN:0363-907X    

DOI:10.1002/er.4440130304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of the exothermic reaction of acetaldehyde with methyl alcohol has been studied using calorimetry in the temperature range of 263–283 K. Based on this study the reaction rate constant for the reaction was found to be\documentclass{article}\pagestyle{empty}\begin{document}$$ k = 1.84\;{\rm x 10}^{- 2} \,\exp \left({- 3527/T} \right) $$\end{document}and the heat of reaction was found to be\documentclass{article}\pagestyle{empty}\begin{document}$$ \left({- \Delta H} \right) = \left({0.3637 - 63.9} \right){\rm kJ/Kg}\,{\rm mole} $$\end{document}These kinetics were based on the assumption of a pseudoisothermal first‐order react

ISSN:0363-907X    

DOI:10.1002/er.4440130305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA brief summary of the simplified continuity, momentum and energy equations that describe heat and mass transfer through unsaturated soil is presented. Classifications of soil water and the hydrodynamic laws governing flow of water through unsaturated soil are discussed. A detailed description of an experimental investigation that was conducted to evaluate certain physical and thermal properties of soil is also included. Specifically, the experiment was to determine the thermal conductivity of moist soil as a function of water content. Another experiment was conducted to study the temperature profiles around a heat source embedded in a bed of moist light clay, the results of which are also presented and shown to be in close agreement with analytically predicted values.The effects of various heat transfer processes as well as the influence of the motion of fluids on heat transfer in an earth bed are presented. Heat diffusion into the soil by conduction is shown to be predominant through the early stages of heating while the liquid water motion contributes to heat transfer during intermediate times and the gas motion is shown to become significant during later stages of drying. The contribution of the convective transport increases with the temperature and becomes equal to the contribution by conduction at moderately high temperatures. Finally, an ‘effective’ or ‘equivalent’ thermal conductivity of the soil is determined. This value helps characterize the heat transfer behaviour of an earth bed as a purely conductive heat transfer

ISSN:0363-907X    

DOI:10.1002/er.4440130306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAnalytical solutions are derived for flow in a semi‐infinite vertical porous medium with heat and mass transfer. When the temperature and mass concentration are uniform a constant pressure is possible and sustains a fully developed flow. Thereafter there is a small perturbation of the wall temperature and concentration, and the subsequent two‐dimensional problem is tackled for large Prandtl number and free convection parameters and small Reynolds number. The heat transfer rate at the wall is discussed quantitativ

ISSN:0363-907X    

DOI:10.1002/er.4440130307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe optimal flat‐plate collector mass flow rate is determined by maximizing the exergy (available energy) delivery of the collector as the objective function. Collector and storage dynamics are neglected. Although the case where the pumping power loss is ignored results in bang‐bang control, the case where this loss is included in the exergy equation results, after some assumptions, in an optimal mass flow rate that is a function of collector parameters, inlet and ambient temperatures and solar heat gain. Daily performance of a typical flat‐plate solar collector with optimum mass flow rate is compared with the performance of the same collector using the mass flow rate obtained by maximizing the difference between the collected thermal energy and the required pumping

ISSN:0363-907X    

DOI:10.1002/er.4440130308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe paper is a first order analytic description of the performance characteristics of a displacement compressor with floating poppet valves. The valves are actuated by the pressure forces acting on them to allow the compressor to deliver compressed gas at any chosen pressure level. The irreversibilities considered are the losses associated with the flow into and out of the cylinder past the valves of the type described. The performance indices of interest are the adiabatic and volumetric efficiencies as they are affected by the mechanical operating speed of the compressor and the chosen pressure ratio. These performance indices are obtained in terms of non‐dimensional parameters which describe the dimensions of the valves and cylinder as well as the operational characteristic

ISSN:0363-907X    

DOI:10.1002/er.4440130309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA two floor hostel for married research scholars consisting of 12 apartments was designed and constructed for the composite climate of Delhi; the design incorporates many passive features. Using modified admittance procedure and Fourier analysis of the periodic parameters, the building was numerically simulated to obtain its thermal performance on an hourly basis. Two apartments of the building (one on the ground floor and one on the first floor have been experimentally monitored by a microprocessor aided data acquisition system. The observations validate the numerical model.

ISSN:0363-907X    

DOI:10.1002/er.4440130310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractCharacteristics of high‐efficiency gas turbine cogeneration systems using low Btu gas (LBG) are first analysed. Raising the turbine inlet temperature and incorporating a regenerator are both investigated as methods to improve the efficiency of the cogeneration system (CGS). Taking a gas obtained by pyrolyzing municipal refuse as an example of an LBG, various thermodynamic characteristics of the CGS are analysed using a simulation model developed by the authors. Secondly, authors investigate the economics of a CGS for district heating and cooling using the pyrolysis gas, making use of the estimated characteristics. It is shown that the CGS is estimated to be economically feasible, whereas a CGS using conventional high Btu fuel gas (methane gas) is estimated to be economically infeasible under assumed conditions. The impacts of changes in various parameters which determine the economics of the CGS are also investigated, and it is shown that the economics of the system using refuse‐recovered LBG can be expected to be further improved owing to future developments in the technology of generating and refining pyrolysis

ISSN:0363-907X    

DOI:10.1002/er.4440130311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY