A Variable Heat Flux Line Source Model For Boreholes In Ground Coupled Heat Pump

It is often reported that a jet fire occurs in industrial installations or in the transportation of hazardous materials and could amplify the scale of accident by imposing lots of heat on people and nearby facilities. This paper presents a new semi-empirical radiation model, namely, the line source model to predict the radiant heat flux distribution around a vertical turbulent hydrocarbon jet flame. In terms of the fact that the jet flame holds the large ratio of flame length to diameter, the new model assumes that all thermal energy is emitted by a line source located inside the jet flame volume. With three typically different shapes to simulate the jet flame shape, a formula is proposed to characterize the profile of the emissive power per line length (EPPLL), by which the line source model can be closed in theory. In comparison with the point source model, the multipoint source model, and the solid flame model, the new model agrees better with the measurement of the heat flux radiated from a small jet flame. It is found that the line source model can well predict the radiant heat flux of both small and large jet flames, yet with the flame shape simulated by the back-to-back cone and the cone–cylinder combined shape, respectively. By parameter sensitivity and uncertainty analysis, the ranking by importance of input parameters is also given for the new model.

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Influence of spatially variable ground heat flux on closed-loop geothermal systems: Line source model with nonhomogeneous Cauchy-type top boundary conditions

Applied Energy ◽

10.1016/j.apenergy.2016.06.074 ◽

2016 ◽

Vol 180 ◽

pp. 572-585 ◽

Cited By ~ 15

Author(s):

Jaime A. Rivera ◽

Philipp Blum ◽

Peter Bayer

Keyword(s):

Heat Flux ◽

Boundary Conditions ◽

Line Source ◽

Closed Loop ◽

Source Model ◽

Cauchy Type ◽

Geothermal Systems ◽

Ground Heat Flux ◽

Line Source Model

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Heat Transfer of Buried Pipe for Heat Pump Application

Journal of Solar Energy Engineering ◽

10.1115/1.2929951 ◽

1991 ◽

Vol 113 (1) ◽

pp. 51-55 ◽

Cited By ~ 21

Author(s):

Viung C. Mei

Keyword(s):

Heat Pump ◽

Line Source ◽

Source Model ◽

The Other ◽

Test Results ◽

Average Deviation ◽

New Model ◽

Source Theory ◽

Soil Temperatures ◽

Line Source Model

It is generally felt that the application of line source theory for ground coil design usually resulted in excessive overdesign. It was anticipated that in order for the ground coil heat pump systems to be economically competitive with other residential heating and cooling systems, ground coil overdesign had to be kept to a minimum. A new ground coil model was derived, which based on energy balance rather than the traditional line source theory. It was aimed to more accurately predict the operation of ground coils. It is the intention of this study to compare this ground coil model with models based on line source theory, a simple line source model and a modified line source model, by using them to simulate the same field test data for both summer and winter ground coil operations. The results indicated that for winter coil operation, the new model predicted the coil liquid exit temperature less than 2°C maximum deviation from the measured values, with an average deviation less than 1°C. The modified line source model had an average deviation of more than 1.5°C. For summer operation, all models underpredicted the measured soil temperatures because the effect of thermal backfill material was not included in the models. The new model still predicted the test results better than the other two models. However, when the effect of sand thermal backfill was included in the new model, which was not easy for the other two models, the calculated soil temperatures were almost identical to the test results.

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Natural convection on a vertical plate with variable heat flux in supercritical fluids

The Journal of Supercritical Fluids ◽

10.1016/j.supflu.2012.12.010 ◽

2013 ◽

Vol 74 ◽

pp. 115-127 ◽

Cited By ~ 17

Author(s):

Ali Reza Teymourtash ◽

Danyal Rezaei Khonakdar ◽

Mohammad Reza Raveshi

Keyword(s):

Heat Flux ◽

Natural Convection ◽

Supercritical Fluids ◽

Vertical Plate ◽

Variable Heat ◽

Variable Heat Flux

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Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

Modern Physics Letters B ◽

10.1142/s0217984916501554 ◽

2016 ◽

Vol 30 (16) ◽

pp. 1650155 ◽

Cited By ~ 9

Author(s):

Ebrahim Afshari ◽

Masoud Ziaei-Rad ◽

Nabi Jahantigh

Keyword(s):

Heat Flux ◽

Fuel Cells ◽

Fuel Cell ◽

Pressure Drop ◽

Flow Field ◽

Pem Fuel Cells ◽

Coolant Flow ◽

Temperature Uniformity ◽

Variable Heat ◽

Variable Heat Flux

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

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