scholarly journals Numerical Modelling of Room Thermal Comfort Conditions

2006 ◽  
Vol 1 ◽  
pp. 347
Author(s):  
S. Gendels ◽  
A. Jakovičs
Keyword(s):  
Heat Balance ◽  
Input Data ◽  
Heat Losses ◽  
Separate Analysis ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Heat Transfers ◽  
Made In ◽  
Building Elements

Particular heat transfer coefficients of building elements gives quantitative notion only about heat losses through this building element. Analysis of the overall heat balance and heat losses of complete building and study of particular contribution of building elements in overall balance allows one to figure out the state of the building and find the building elements of bounding construction with most significant heat losses. Project variants of the buildings (or rebuilding in case of renovation), which ensure the desirable economy of energy and proportions of investments can be find varying the proportions of the surface area of building elements (e.g., windows and doors). A lot of factors can be included in requirements of heat consumption of the building. Moreover, monthly calculations are possible. These both aspects contribute in so called method of full calculations, which is made in correspondence with standard EN 832. Though, it is possible to use also the simplified variant of calculations offered by Latvian building normative LBN 002-01. Both approaches of modelling are realised in elaborated software HeatMod, which is made in laboratory of MMTEP. Both methodologies are applicable to buildings, which can be divided in separate blocks in such a way that temperature in each of blocks is approximately constant or exists different number of floors in each of blocks. Separate analysis of heat balance is made for each block and finally the obtained heat consumptions are summed together. This allows one to consider really existing temperature difference in building, e.g., in office and depository. It is possible to approximate also the influence of given regime of temperature. The possibility to minimise heat losses and their contributions are analysed on particular examples. Comparative analysis of both methods is performed and the dependence of various heat transfers on the change of different input data are studied.

Experimental Platforms and Finite Element Analysis on Hot Stamping Processes

2014 ◽  
Vol 1063 ◽  
pp. 334-338 ◽  
Author(s):  
Tzu Hao Hung ◽  
Heng Kuang Tsai ◽  
Fuh Kuo Chen ◽  
Ping Kun Lee
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Process Design ◽  
Hot Stamping ◽  
Boron Steel ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
The Finite Element Analysis

Due to the complexity of hot stamping mechanism, including the coupling of material formability, thermal interaction and metallurgical microstructure, it makes the process design more difficult even with the aid of the finite element analysis. In the present study, the experimental platforms were developed to measure and derive the friction and heat transfer coefficients, respectively. The experiments at various elevated temperatures and contact pressures were conducted and the friction coefficients and heat transfer coefficients were obtained. A finite element model was also established with the experimental data and the material properties of the boron steel calculated from the JMatPro software. The finite element simulations for the hot stamping forming of an automotive door beam, including transportation analysis, hot forming analysis and die quenching analysis were then performed to examine the forming properties of the door beam. The validation of the finite element results by the production part confirms the efficiency and accuracy of the developed experimental platforms and the finite element analysis for the process design of hot stamping.

Calculation of Hourly Output of a Solar Still

1993 ◽  
Vol 115 (4) ◽  
pp. 231-236 ◽  
Author(s):  
V. B. Sharma ◽  
S. C. Mullick
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Balance ◽  
Solar Still ◽  
Balance Equations ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Hourly Output ◽  
The Heat Balance

An approximate method for calculation of the hourly output of a solar still over a 24-hour cycle has been studied. The hourly performance of a solar still is predicted given the values of the insolation, ambient temperature, wind heat-transfer coefficient, water depth, and the heat-transfer coefficient through base and sides. The proposed method does not require graphical constructions and does not assume constant heat-transfer coefficients as in the previous methods. The possibility of using the values of the heat-transfer coefficients for the preceding time interval in the heat balance equations is examined. In fact, two variants of the basic method of calculation are examined. The hourly rate of evaporation is obtained. The results are compared to those obtained by numerical solution of the complete set of heat balance equations. The errors from the approximate method in prediction of the 24-hour output are within ±1.5 percent of the values from the numerical solution using the heat balance equations. The range of variables covered is 5 to 15 cms in water depth, 0 to 3 W/m2K in a heat-transfer coefficient through base and sides, and 5 to 40 W/m2K in a wind heat-transfer coefficient.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

scholarly journals Thermal Characteristics Analysis for Motorized Spindle System of CNC Machining Center

2019 ◽  
Vol 257 ◽  
pp. 02003
Author(s):  
Xiaolei Deng ◽  
Xinghui Zhang ◽  
Mucheng Zhang ◽  
Yibo Zhou ◽  
Huan Lin ◽  
...  
Keyword(s):  
Thermal Characteristics ◽  
Thermal Error ◽  
Cnc Machining ◽  
Transfer Coefficients ◽  
Motorized Spindle ◽  
Element Analysis ◽  
Spindle System ◽  
Heat Transfer Coefficients ◽  
Machining Center ◽  
Characteristics Analysis

Based on the comprehensive analysis of the heat sources of the motorized spindle system, the thermal loads, including the heat generation of bearing friction and the electromagnetic loss of the built-in motor, are carried out for a machining center motorized spindle system. And then, the convective heat transfer coefficients of the whole spindle system are analyzed. The thermal characteristics of the motorized spindle system are calculated by finite element analysis. The steady state temperature field distribution of the motorized spindle is obtained. It provides some references for improving the thermal characteristics of the motorized spindle and reducing the difficulty of thermal error compensation.

Mass Transfer Technique for Investigation of Heat Transfer by Jet-Impingement Systems

1972 ◽  
Vol 14 (6) ◽  
pp. 389-392 ◽  
Author(s):  
J. Ward ◽  
F. J. K. Ideriah ◽  
S. D. Probert ◽  
A. Duggan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfers

The technique of using mass transfer measurements (by sublimation of naphthalene) together with the Chilton–Colburn analogy is shown to be feasible for evaluation of heat transfers from impinging jets. The method is then used to determine heat transfer coefficients at the burner walls in models of jet–impingement furnaces.

Squeal and Thermal Analysis of Automobile Disc Brake Rotors

2015 ◽  
Vol 764-765 ◽  
pp. 369-373
Author(s):  
Wei Hsin Gau ◽  
Kun Nan Chen ◽  
Chin Yuan Hung
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Cast Iron ◽  
Cfd Simulation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Brake Rotors

The brakes of an automobile are among the most critical components regarding the safety features, and disc brakes are the most common type used in passenger vehicles. In this research, the squeal phenomena of a swirl-vent brake rotor and the thermal analysis of two straight-vent brake rotors, made of cast-iron and aluminum-alloy, are investigated. For the squeal analysis, finite element models are created and analyzed using a prestressed modal analysis with complex eigen-solutions. For the thermal analysis, heat transfer coefficients on the surfaces of a rotor as functions of time are first estimated by CFD simulation, and then imported to a thermal analysis program as the boundary condition. Finally, the temperature distribution of the rotor can be calculated by finite element analysis. The simulation results show that vortices will arise in the vented passages of straight-vent rotors, which means less heat carried away and lower heat transfer coefficients. The swirl-vent brake design is clearly better for thermal ventilation. Furthermore, under the same condition, aluminum-alloy rotors exhibit more uniform temperature distributions with smaller temperature gradients than cast-iron rotors do.

Modeling of Wellbore Overall Heat Transfer in Circulation

2012 ◽  
Vol 260-261 ◽  
pp. 537-542
Author(s):  
Hui Fang Song ◽  
Rui He Wang ◽  
Hong Jian Ni
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Steady State ◽  
Radial Direction ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Temperature Calculation ◽  
Wellbore Pressure ◽  
Film Heat Transfer

Heat is transferred between the fluid and the surroundings in the wellbore. Quantitative knowledge of wellbore heat transfer is important in drilling and production operations. A new model of wellbore heat transfer using finite element analysis is developed in this study. This solution assumes the heat transfer in the wellbore is steady state and only happens in radial direction. The model considers heat gained due to wellbore pressure loss in circulation, which is more accurate in temperature calculation. The overall heat resistance in the wellbore is analyzed, taking into account the film heat transfer coefficients difference between the tube and the annulus. Previous literature has been reviewed to determine the correlation which can be used in the model.

scholarly journals Uncoupled CFD-FEA Methods for the Thermo-Structural Analysis of Turbochargers

2019 ◽  
Vol 4 (4) ◽  
pp. 39
Author(s):  
Piotr Łuczyński ◽  
Matthias Giesen ◽  
Thomas-Sebastian Gier ◽  
Manfred Wirsum
Keyword(s):  
Heat Transfer ◽  
Accurate Determination ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Mechanical Analysis ◽  
Heating Process ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Thermally Induced ◽  
Heat Transfer Coefficients

In turbocharger design, the accurate determination of thermally induced stresses is of particular importance for life cycle predictions. An accurate, transient, thermal finite element analysis (FEA) of turbocharger components requires transient conjugate heat transfer (CHT) analysis. However, due to the vastly different timescales of the heat transfer mechanisms in fluid and in solid states, unsteady CHT simulations are burdened by high computational costs. Hence, for design iterations, uncoupled CFD and FEA approaches are needed. The quality of the uncoupled thermal analysis depends on the local heat transfer coefficients (HTC) and reference fluid temperatures. In this paper, multiple CFD-FEA methods known from literature are implemented in a numerical model of a turbocharger. In order to describe the heat transfer and thermal boundary layer of the fluid, different definitions of heat transfer coefficients and reference fluid temperatures are investigated with regard to calculation time and accuracy. For the transient simulation of a long heating process, the combination of the CFD-FEA methods with the interpolation FEA approach is examined. Additionally, a structural-mechanical analysis is conducted. The results of the developed methods are evaluated against experimental data and the results of the extensive unsteady CHT numerical method.

The use of heat transfer coefficients in estimating sensible heat loss from the pig

1977 ◽  
Vol 25 (3) ◽  
pp. 271-279 ◽  
Author(s):  
L. E. Mount
Keyword(s):  
Heat Transfer ◽  
Body Weight ◽  
Heat Loss ◽  
Radiant Heat ◽  
Heat Losses ◽  
Sensible Heat ◽  
Transfer Coefficients ◽  
Wind Speeds ◽  
Heat Transfer Coefficients ◽  
Environmental Temperatures

SUMMARYHeat transfer coefficients are used to calculate convective and radiant heat losses from pigs of 4, 20 and 60 kg body weight at 20 and 30 °C environmental temperatures for different wind speeds. Comparisons with heat losses estimated from whole-animal calorimetry suggest that calculations with heat transfer coefficients can lead to useful approximate estimates of heat loss from the pig.

scholarly journals Application of Mathematical Models in Analysis of Heat Losses in the Buildings

2006 ◽  
Vol 1 ◽  
pp. 341
Author(s):  
S. Gendels
Keyword(s):  
Heat Transfer ◽  
Thermal Comfort ◽  
Heat Balance ◽  
Heat Transfer Process ◽  
Heat Losses ◽  
Balance Model ◽  
Living Room ◽  
Transfer Coefficients ◽  
Multiple Parameters ◽  
Quantity Of Heat

Physical model of heat balance for separate living room is discussed, which allows to analyse the distributions of the flow of air and temperature depending on the physical conditions and geometry. The model enables to choose the optimal surface area of building elements and their properties in order to decrease the heat losses and improve the conditions of thermal comfort. Room with bounding constructions and real dimensions is modelled that helps to understand the peculiarities of heat transfer process in the room as well as distribution of various characteristic quantities and their dependence on the different conditions. Multiple parameters are varied in 2D calculations and their influence on the distributions of temperature and velocity fields is analysed, which characterises the conditions of the thermal comfort. On the basis of considered model, the quantity of heat has been estimated that inflows or outflows through the bounding constructions. The power of convector is estimated, too, at a given temperature of the surface of convector. It is possible to estimate the heat transfer coefficients of the surfaces of bounding constructions with various properties, what requires considerable effort in real conditions of exploitation. One of the conditions of comfort is the temperature difference between frontal walls of the room – it should be less than some degrees. Essential role is played also by the intensity of air flow mostly because it increases heat transfer. Hence, flows between the room and outside environment are created with significant heat losses (so called convective heat losses). The influence of various geometric parameters on the character of the flow of air is analysed. The software ANSYS/FLOTRAN 5.5, where the turbulence is described by k- ? model, has been used for the elaboration of the heat balance model of the room.

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