ISSN:0145-7632    

DOI:10.1080/014576300271103

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Data collected from the open literature plus some new, unpublished data show that the exit condition with in-tube condensation can change the flow regimes, introduce certain types of instabilities, and alter flooding velocities. All the possible orientations are considered: horizontal, vertical with vapor downflow, and vertical with vapor upflow (refluxing).

ISSN:0145-7632    

DOI:10.1080/014576300271112

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A skin cooling system has been developed to reject heat from high-power electronic equipment onboard an aircraft. In this system, the heat is rejected through the aircraft skin by use of internal skin ducts with enhanced surfaces. Heat transfer through the skin and the air flow in the system have been modeled and experimentally verified in the laboratory environment. In addition, the effect of the ducting system on the performance of the electronic equipment has been characterized. This article describes a series of tests that were performed to verify the modeling assumptions for heat dissipation from and air flow through the equipment. The tests were performed using the actual electronic equipment in a representative cabin configuration and at cabin conditions. Results show that the equipment operates at a higher temperature at cabin conditions than at room conditions. This is due to the constant volumetric flow throughput of the equipment fan at higher altitudes but lower mass flow rate (i.e., lower density) at cabin conditions. Furthermore, the equipment back-pressure produced by the cooling system adds to the heating of the equipment. The compatibility of the equipment fan is also critical in the stacking arrangement of the equipment.

ISSN:0145-7632    

DOI:10.1080/014576300271121

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

This article describes an experimental investigation to study the effect of guide vanes on the heat transfer coefficient over the unfinned frame of an externally cooled induction motor. Guide vanes with various heights and spacings have been tested. In general, the guide vanes modify the air flow over the frame, hence increasing the heat transfer coefficient. An optimum heat transfer case is found, for which the average heat transfer coefficient is 70% higher than for the case without guide vanes. The velocity distributions of the air flow are measured for comparison with the heat transfer coefficient fields. The location of the terminal box is optimized, resulting in a 1° drop in the average temperature rise of the coil motor. Finally, the results of this research are applied to a real induction motor and its average coil temperature becomes 9° lower than that of a commercial motor.

ISSN:0145-7632    

DOI:10.1080/014576300271130

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The present work introduces a transient endoreversible model of a heat-driven refrigeration plant, which is driven by a fuel-burning heater. The model consists of a combustion chamber with negligible heat loss to the ambient, a refrigerator with three finite-size heat exchangers, namely, the evaporator between the refrigeration load and refrigerant, the condenser between the refrigerant and the ambient, and the generator between the combustion chamber and the refrigerant, and finally the refrigerated space. The total thermal conductance of the three heat exchangers is fixed. A thermodynamic optimization of the absorption cycle is then performed, reporting the operating conditions for minimum time to reach a prescribed cold-space temperature, thus maximum refrigeration rate, specifically, the optimal mass fuel flow rate and the optimal way of allocating the thermal conductance inventory. Half of the total supply of thermal conductance has to be divided equally between the generator and evaporator and the other half allocated to the condenser, for optimal operation. A narrow range of fuel flow rates lead to the minimum time to achieve a prescribed cold-space temperature, thus stressing the importance of the transient analysis. Appropriate dimensionless groups were identified and the generalized results are reported in dimensionless charts.

ISSN:0145-7632    

DOI:10.1080/014576300271149

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A study of the thermodynamic performance of nonazeotropic refrigerant mixtures (NARMs) involving R-143a/R-134a was completed. The aim of the study was to identify possible replacements for R-12. Two refrigeration cycles were considered, the vapor-compression cycle and the internal heat exchanger cycle. Our results suggest that the nonazeotropic R-143a/R-134a mixtures studied yield comparable performance to R-12 when the internal heat exchanger cycle is used.

ISSN:0145-7632    

DOI:10.1080/014576300271158

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Predictions are carried out for radiation heat flux incident on a base surface from a gaseous conical plume with radial and axial temperature variations. A forward Monte Carlo method is developed and validated by comparing the results of an isothermal cylindrical plume, a conical plume with axial temperature variations, and a cylindrical gas-filled space. The minimum number of random emission sites in the plume required to obtain reasonable estimates of heat flux is determined. The radial temperature variations in the plume are shown to result in significant reduction in heat flux. The method assumes the plume to be gray and therefore the spectral dependence of plume properties is not considered.

ISSN:0145-7632    

DOI:10.1080/014576300271167

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/014576300271176

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/01457630050127991

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/01457630050128008

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor