Impact of the filling level on the global heat transfer coefficient of a plate cross section for sorption heat pumps

2017 ◽  
Author(s):  
Florine Giraud ◽  
Yacine Hamitouche ◽  
Pierrick Vallon ◽  
Brice Tremeac
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Heat Pumps ◽  
Sorption Heat

scholarly journals Local Heat Transfer Analysis in a Single Microchannel with Boiling DI-Water and Correlations with Impedance Local Sensors

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6473
Author(s):  
Mohammadmahdi Talebi ◽  
Sahba Sadir ◽  
Manfred Kraut ◽  
Roland Dittmeyer ◽  
Peter Woias
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Flow Boiling ◽  
Rectangular Cross Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Experimental Conditions ◽  
Impedance Measurements

Determination of local heat transfer coefficient at the interface of channel wall and fluid was the main goal of this experimental study in microchannel flow boiling domain. Flow boiling heat transfer to DI-water in a single microchannel with a rectangular cross section was experimentally investigated. The rectangular cross section dimensions of the experimented microchannel were 1050 μm × 500 μm and 1500 μm × 500 μm. Experiments under conditions of boiling were performed in a test setup, which allows the optical and local impedance measurements of the fluids by mass fluxes of 22.1 kg·m−2·s−1 to 118.8 kg·m−2·s−1 and heat fluxes in the range of 14.7 kW·m−2 to 116.54 kW·m−2. The effect of the mass flux, heat flux, and flow pattern on flow boiling local heat transfer coefficient and pressure drop were investigated. Experimental data compared to existing correlations indicated no single correlation of good predictive value. This was concluded to be the case due to the instability of flow conditions on one hand and the variation of the flow regimes over the experimental conditions on the other hand. The results from the local impedance measurements in correlation to the optical measurements shows the flow regime variation at the experimental conditions. From these measurements, useful parameters for use in models on boiling like the 3-zone model were shown. It was shown that the sensing method can shed a precise light on unknown features locally in slug flow such as residence time of each phases, bubble frequency, and duty cycle.

Passive House and Construction Standard: Example Design and Multi-Objective Optimization

2015 ◽  
Vol 719-720 ◽  
pp. 177-180
Author(s):  
Kağan Poyraz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Thermal Insulation ◽  
Multi Objective Optimization ◽  
Passive House ◽  
Multi Objective ◽  
The Cross ◽  
Set Up

Due to environmental and energy matters, importance of future construction trend-Passive House Design is increasing all over the world. In Europe, already recommended values ​​for passive buildings are included in thermal insulation standards and energy regulation directives. There is a wide range of construction materials nowadays. The key point is using proper techniques by harmonizing correct practice and materials. In this regard, smart optimization set-up approach is necessary in order to achieve the most suitable design which has the lowest CO2 and SO2 values and appears as the cheapest option. The sample given in this paper is an example of an exterior wall design for residential passive houses (heat transfer coefficient (U) value through the cross section is 0,108 W/m²K). Connected with the aim of the paper, which is showing an multi-objective optimization method for choosing the best thermal insulation design in the case of that more than one projection, results of given example design in the paper is used. Simultaneously, criteria of total thickness, heat transfer coefficient (U) through the cross section, global warming potential (GWP), acid produce (AP), primary energy content (PEI) non renewable and cost in 2013 per m2 are included in “Smart optimization set-up approach diagram”.

scholarly journals Modeling and Analysis of a Coated Tube Adsorber for Adsorption Heat Pumps

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6878
Author(s):  
João M. S. Dias ◽  
Vítor A. F. Costa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Working Conditions ◽  
Fluid Velocity ◽  
Heat Pumps ◽  
Heating Power ◽  
Adsorption Heat ◽  
Coefficient Of Performance ◽  
Water Heating

This work investigates the effects of several parameters on the coefficient of performance (COP) and the specific heating power (SHP) of a coated-tube adsorber for adsorption heat pumps (AHP) suitable for water heating (space and/or domestic water heating). The COP and SHP are obtained based on physical models that have already been proven to adequately describe this type of adsorber. Several parameters are tested, namely, the regeneration, condenser and evaporator temperatures, the heat transfer fluid velocity, the tube diameter, the adsorbent coating thickness, the metal–adsorbent heat transfer coefficient, and the cycle time. Two different scenarios were tested, corresponding to distinct working conditions. The working conditions for Scenario A are suitable for pre-heating water in mild climates. Scenario B’s working conditions are based on the European standard EN16147. The maximum COP is obtained for regeneration temperatures of 75 °C and 95 °C for Scenarios A and B, respectively. The COP increases for longer cycle times (more complete adsorption and desorption processes) whilst the SHP decreases (less complete cycles by unit time). Hence, the right balance between the COP and the SHP must be found for each particular scenario to have the best whole performance of the AHP. A metal–adsorbent heat transfer coefficient lower than 200 W·m−2·K−1 leads to reduced SHP. Lower adsorbent coating thicknesses lead to higher SHP and can still provide reasonably high COP. However, low coating thicknesses would require a too-high number of tubes to achieve the desired adsorbent mass to deliver the required useful heating power, resulting in too-large systems. Due to this, the best relationship between the SHP and the size of the system must be selected for each specific application.

A Method for the Determination of the Local Turbulent Friction Factor and Heat Transfer Coefficient in Generalized Geometries

1971 ◽  
Vol 93 (1) ◽  
pp. 61-68 ◽  
Author(s):  
E. Aranovitch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Arbitrary Cross Section ◽  
Transfer Coefficients ◽  
Turbulent Friction ◽  
Heat Transfer Coefficients

A method is presented for the determination of the distributions of velocity, local friction, and heat transfer coefficients in a forced axial turbulent flow with an arbitrary cross section. The method uses as basis the characteristics of the laminar flow. A comparison is made with some experimental results concerning different geometries.

Numerical investigation of CuO-water nanofluid turbulent convective heat transfer in square cross-section duct under constant heat flux

2016 ◽  
Vol 33 (6) ◽  
pp. 1714-1728 ◽  
Author(s):  
Hsien-Hung Ting ◽  
Shuhn-Shyurng Hou
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Cross Section ◽  
Convective Heat ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Content Type

Purpose – The purpose of this paper is to numerically investigate the convective heat transfer of water-based CuO nanofluids flowing through a square cross-section duct under constant heat flux in the turbulent flow regime. Design/methodology/approach – The numerical simulation is carried out at various Peclet numbers and particle concentrations (0.1, 0.2, 0.5, and 0.8 vol%). The finite volume formulation is used with the semi-implicit method for pressure-linked equations algorithm to solve the discretized equations derived from the partial nonlinear differential equations of the mathematical model. Findings – The heat transfer coefficients and Nusselt numbers of CuO-water nanofluids increase with increases in the Peclet number as well as particle volume concentration. Also, enhancement of the heat transfer coefficient is much greater than that of the effective thermal conductivity at the same nanoparticle concentration. Research limitations/implications – Simulation of nanofluids turbulent forced convection at very high Reynolds number is worth for further study. Practical implications – The heat transfer rates through non-circular ducts are smaller than the circular tubes. Nevertheless, the pressure drop of the non-circular duct is less than that of the circular tube. This study clearly presents that the nanoparticles suspended in water enhance the convective heat transfer coefficient, despite low volume fraction between 0.1 and 0.8 percent. Adding nanoparticles to conventional fluids may enhance heat transfer performance through the non-circular ducts, leading to extensive practical applications in industries for the non-circular ducts. Originality/value – Few papers have numerically studied convective heat transfer properties of nanofluids through non-circular ducts. The present numerical results show a good agreement with the published experimental data.

scholarly journals Heat transfer coefficient in elliptical tube at the constant heat flux

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1323-1332
Author(s):  
Stanislaw Lopata ◽  
Pawel Oclon ◽  
Tomasz Stelmach ◽  
Pawel Markowski
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Measurement Data ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Constant Heat ◽  
The Heat Transfer Coefficient

Cross-flow heat exchangers with elliptical tubes are often used in industrial application. In comparison with round tubes, the elliptical tubes have a better aero-dynamic shape, which results in a lower pressure drop of working fluid flowing through the inter-tubular space of heat exchanger. Also, a higher heat flux is transferred from gas to the wall of such a tube due to the more intense heat exchange process. To prove this thesis, the values of the heat transfer coefficient from the wall of the elliptical pipe to the water flowing inside were determined, using the data from the conducted measurements. This study presents also research stand with a vertically positioned tube. In order to obtain a constant heat flux through the wall of elliptical tube, a resistance wire is used, evenly wound on the external surface of tube measuring section. The use of thermal insulation minimized heat loss to the environment to a negligible value. Installed K-type thermocouples allowed one to obtain, for various measurement conditions, the temperature distribution within the elliptical tube wall (for a given cross-section) and the water flowing inside it (in a given cross-section, at different depths, for both axes of the ellipse). The design of the stand allows such measurements in several locations along the length of the measurement section. The measurement results were used to verify numerical calculations. The relative error of the heat transfer coefficient value determined on the basis of CFD calculations using the SST-TR turbulence model in relation to the one determined on the basis of the measurement data is about 11%.

Measurement of the Heat Transfer Coefficient for Mercury Flowing in a Narrow Channel

2002 ◽  
Vol 124 (6) ◽  
pp. 1034-1038 ◽  
Author(s):  
J. M. Crye ◽  
A. E. Ruggles ◽  
W. D. Pointer ◽  
D. K. Felde ◽  
P. A. Jallouk ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Narrow Channel ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
The Heat Transfer Coefficient

The heat transfer coefficient is inferred from measurements for mercury flowing in a channel of cross-section 2 mm×40 mm with flow velocities from 1 m/s to 4 m/s and heat fluxes from 192 kW/m2 to 1.14 MW/m2. Mercury bulk temperatures vary from 67°C to 143°C. Inferred heat transfer coefficients agree with open literature tube data when compared on a Nusselt versus. Peclet number plot, with Nusselt numbers examined from 8 to 17 and Peclet numbers examined from 790 to 3070.

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