scholarly journals Validation of radiant and convective heat transfer models of photonic membrane using non-invasive imaging of condensation pattern

2021 ◽  
Vol 2069 (1) ◽  
pp. 012100
Author(s):  
E Teitelbaum ◽  
D Aviv ◽  
M Hou ◽  
J Li ◽  
A Rysanek ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Thermal Stratification ◽  
Radiative Heat ◽  
Membrane Surface ◽  
Standard Technique ◽  
View Factor ◽  
Non Invasive ◽  
Radiant Cooling ◽  
Condensation Pattern

Abstract Cooling a sample of a material until condensation is observed is a standard technique for accurately measuring the dewpoint and associated relative humidity in a volume. When conducting an experiment with a membrane-assisted radiant cooling panel, we found that membrane surface temperatures were difficult to measure directly. Instead, the onset of condensation was used to infer the membrane’s surface temperature. However, the radiant cooling panels displayed variations of membrane surface temperature at steady state, and thus a resulting condensation contour was observed, forming a curve on which the membrane surface temperature was accurately known and constant - the dewpoint. The curve was in equilibrium between the internal panel temperature driven by internal free convection in the air gap and the view factor to surrounding surfaces, which can be evaluated at each point along the curve. In this paper, we assess the convective and radiative heat transfer balances using simulations. Our methods expand the “sensing” of condensation to provide information about view factor and thermal stratification, both of which are quantities that are difficult to measure adequately in the field.

scholarly journals A numerical model and validation of phase change material integrated thermoelectric radiant cooling panel

2019 ◽  
Vol 111 ◽  
pp. 01001
Author(s):  
Hansol Lim ◽  
Hye-Jin Cho ◽  
Seong-Yong Cheon ◽  
Soo-Jin Lee ◽  
Jae-Weon Jeong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Model ◽  
Surface Temperature ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Overall Heat Transfer Coefficient ◽  
Radiant Cooling ◽  
Change Material

A phase change material based radiant cooling panel with thermoelectric module (PCM-TERCP) is proposed in this study. It consists of two aluminium panels, and phase change materials (PCMs) sandwiched between the two panels. Thermoelectric modules (TEMs) are attached to one of the aluminium panels, and heat sinks are attached to the top side of TEMs. PCM-TERCP is a thermal energy storage concept equipment, in which TEMs freeze the PCM during the night whose melting temperature is 16○C. Therefore, the radiant cooling panel can maintain a surface temperature of 16◦C without the operation of TEM during the day. Furthermore, it is necessary to design the PCM-TERCP in a way that it can maintain the panel surface temperature during the targeted operating time. Therefore, the numerical model was developed using finite difference method to evaluate the thermal behaviour of PCM-TERCP. Experiments were also conducted to validate the performance of the developed model. Using the developed model, the possible operation time was investigated to determine the overall heat transfer coefficient required between radiant cooling panel and TEM. Consequently, the results showed that a overall heat transfer coefficient of 394 W/m2K is required to maintain the surface temperature between 16○C to 18○C for a 3 hours operation.

scholarly journals A Deep Neural Network Model of Particle Thermal Radiation in Packed Bed

2020 ◽  
Vol 34 (01) ◽  
pp. 1029-1036
Author(s):  
Hao Wu ◽  
Shuang Hao
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Power Plants ◽  
Deep Neural Network ◽  
Radiative Heat ◽  
Particle Packing ◽  
View Factor ◽  
Pebble Bed

Prediction of particle radiative heat transfer flux is an important task in the large discrete granular systems, such as pebble bed in power plants and industrial fluidized beds. For particle motion and packing, discrete element method (DEM) now is widely accepted as the excellent Lagrangian approach. For thermal radiation, traditional methods focus on calculating the obstructed view factor directly by numerical algorithms. The major challenge for the simulation is that the method is proven to be time-consuming and not feasible to be applied in the practical cases. In this work, we propose an analytical model to calculate macroscopic effective conductivity from particle packing structures Then, we develop a deep neural network (DNN) model used as a predictor of the complex view factor function. The DNN model is trained by a large dataset and the computational speed is greatly improved with good accuracy. It is feasible to perform real-time simulation with DNN model for radiative heat transfer in large pebble bed. The trained model also can be coupled with DEM and used to analyze efficiently the directional radiative conductivity, anisotropic factor and wall effect of the particle thermal radiation.

Eight Surfaces of Radiation Heat Transfer Network Model Development

2013 ◽  
Vol 391 ◽  
pp. 191-195 ◽  
Author(s):  
Ummi Kalthum Ibrahim ◽  
Ruzitah Mohd Salleh ◽  
W. Zhou
Keyword(s):  
Heat Transfer ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Radiative Heat ◽  
Radiation Heat Transfer ◽  
Model Development ◽  
Transfer Model ◽  
View Factor ◽  
Radiation Heat

This paper deals with the numerical solution for radiative heat transfer within a heated six wall surfaces baking oven, baking tin surface and bread surface. The radiation heat transfer model is constructed by adopting a radiation network representation analysis. The analysis applies view factor and radiosity in determining the radiation rates for each surface in the oven. The amount of radiation heat, q and temperature, T variables are equivalent to electric current and voltage, respectively. Finite difference method coupled with Gauss-Seidel iteration was selected to solve the equations involved in the analysis. Even though this method is tedious and intractable for multiple surfaces, but it would seem to be the most accurate and suitable approach for radiation analysis in the enclosure.

scholarly journals Method for calculation of radiative heat transfer in beds of spherical particles

2020 ◽  
Vol 63 (6) ◽  
pp. 680-688
Author(s):  
A. I. Malinouski
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Direct Calculation ◽  
Computational Effort ◽  
Spherical Particles ◽  
Radiative Heat Flux ◽  
View Factor ◽  
Discrete Elements

A new technique for implementing external (particle-to-wall) and particle-to-particle radiative heat transfer in discrete elements method (DEM) simulations is proposed. It is based on the idea that an expected view factor value depends on relevant local bed parameters (distance between particles, particle radius ratio, and local bed porosity). Calculation of average view factors via the formula requires considerably less computational effort than direct in situ integration, when this happens a reasonable average value and an overall accuracy comparable to direct calculation are provided. Both mono- and polydisperse mixtures of spherical opaque particles were considered. It was shown that using nondimensional parameters, a simple general dependence for an external radiative heat flux may be introduced. Exponential and linear fits were proposed for estimating the particle-particle radiative heat flux. The generalization of the obtained formulas for various bed porosities is proposed. The distribution of cumulative transferred heat flux across the particles up to a certain distance was found, and the recommendations regarding the choice of that parameter to achieve a desired accuracy were formulated. Also, the method to account for the particle emissivity was proposed on the basis of the empirical dependence between emissivity and radiative heat flux in porous materials. The proposed method satisfies all the requirements to become a standard implementation of radiative heat transfer calculation in DEM.

Analytical Models for Radiative Heat Transfer in Radioisotope Thermophotovoltaic (RTPV) Cell

2011 ◽  
Author(s):  
Prabodh Panindre ◽  
Narges Susan Mousavi Kh. ◽  
Sunil Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Cell Surface ◽  
Surface Temperature ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Heat Flux ◽  
Emitter Surface ◽  
Surface Temperatures ◽  
Pv Cell

A Radioisotope Thermophotovoltaic (RTPV) Cell is a device used to convert heat energy into electrical energy. The electric generation capacity of RTPV cell depends on the radiative heat transfer between its two surfaces: the emitter surface heated by radioisotope thermal source and the receiving photovoltaic (PV) cell surface. The spectral directional surface properties and the surface temperatures of emitter and PV cell surface play important roles in quantifying the radiative heat flux of RTPV cell. This paper establishes the required analytic flat plate solutions to calculate the radiative heat flux of RTPV cell. The results obtained using the analytic solutions developed in this study have been qualitatively validated with the results of numerical simulations performed by a commercially available software. The effect of the surface temperatures and emitter surface coating on RTPV cell capacity is also studied and analyzed by both the methods. The results obtained from both the methods show that PV cell surface temperature has negligible effect on RTPV cell capacity as compared to the emitter surface temperature. Also, the radiative heat flux of RTPV cell with coated emitter is found to be significantly higher than that of RTPV cell with uncoated emitter surface. The analytical methods can be used to estimate the net radiative heat flux of RTPV cell for different surface temperatures and are independent of the dimensions of RTPV cell.

Numerical Sensitivity and View Factor Calculation Using the Monte Carlo Method

2006 ◽  
Vol 220 (5) ◽  
pp. 697-702 ◽  
Author(s):  
M. R. Vujičić ◽  
N. P. Lavery ◽  
S. G. R. Brown
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Radiative Heat ◽  
Interesting Case ◽  
View Factor ◽  
Cpu Time ◽  
The Monte Carlo Method ◽  
Discretization Schemes ◽  
Time Accuracy

In radiative heat transfer simulations, the geometrical view (configuration, form) factor plays a crucial role. Several different methods (deterministic and non-deterministic) such as integration, the Monte Carlo method, and the Hemi-Cube method have been introduced to calculate view factors in recent years. In this article, the Monte Carlo method combined with the finite-element (FE) technique is investigated. Results describing the relationships among different discretization schemes, number of rays used for the view factor calculation, CPU time, accuracy, and two origins of emanating rays are presented. The interesting case where reduced accuracy is obtained with increased refinement of FE mesh is discussed.

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