Location Of Heat Source Research Articles

Optimization of the location of multiple discrete heat sources in a ventilated cavity using artificial neural networks and micro genetic algorithm

This work is aimed at evaluating the optimal location of three discrete heat sources which could be placed anywhere inside a ventilated cavity and cooled by forced convection. The computational domain involves a square cavity with adiabatic walls, diagonally opposite inlet and outlet, with a heat flux of 1000 W/m 2 on the heat sources and constant velocity of 4 m/s at the inlet. The two dimensional flow and temperature fields are obtained by performing simulations on FLUENT 6.3. The micro genetic algorithm (MGA) using the six coordinates of the heat sources as input parameters and 5 individuals in a population is used for the optimization, with the objective function as minimizing the maximum temperature on any of the heat sources. Initially for 66 generations, simulations were repeatedly done to evaluate the objective function. This data was used to train a back-propagation artificial neural network (ANN) using the Bayesian regularization algorithm to predict the fitness from the six inputs. This trained ANN was integrated with the micro genetic algorithm to evolve the population for 1000 generations to arrive at the global optimum. Sensitivity studies have been carried out on the optimal solution by varying the Reynolds number. This study shows that by integrating ANN with GA, the computational time can be reduced substantially in problems of this class.

Personal Exposure Between People in a Room Ventilated by Textile Terminals—with and without Personalized Ventilation

This paper describes an investigation made in a room ventilated by an air distribution system based on a textile terminal. The air distribution in the room is mainly controlled by buoyancy forces from the heat sources, although the flow from the textile terminal can be characterized as a displacement flow with a downward direction in areas of the room where no thermal load is present. The system was extended by a personalized ventilation system to study the improved protection of people in a room. The investigation involved full-scale experiments with two breathing thermal manikins. One manikin is the source and the other the target. In general it was found that when the air is supplied from the textile terminal alone, the flow in the room is fully mixed with limited protection of the occupants. Selected locations of supply, return, and heat sources can produce a displacement flow in the room with increased protection of the occupants. It is shown that personalized ventilation improves the protection of occupants by increasing the personal exposure index.

An investigation into fixed-bed microreactors using lattice Boltzmann method simulations

The fixed-bed microreactor is an important component in many biochip, microsensor, and microfluidic devices. The lattice Boltzmann method (LBM) provides a powerful technique for investigating such microfluidic systems. Accordingly, this study performs LBM-based simulations to examine fluid flows through a fixed-bed microreactor comprising a microarray of porous solids. During operation, the fluid and porous solid species are heated to prompt the chemical reaction necessary to generate the required products. Using the LB model, the flow fields and temperature fields in the microreactor are simulated for different Reynolds numbers, heat source locations, the reacting block aspect ratios, and porosity. A simple model is proposed to evaluate the chemical reactive efficiency of the microreactor based on the steady-state temperature field. The results of this model enable the optimal configuration and operating parameters to be established for the microreactor.

The effect of internal heat source and opening locations on environmental natural ventilation

Two-dimensional computational simulations are performed to examine the effect of open location on natural ventilation for room with an internal heat source. The room is symmetrically cooled from the sides and insulated from lower and upper walls. The analysis of the fluid flow and heat transfer characteristics of the natural ventilation was carried out by the method of streamline and temperature contours. Three different cases of local open length on lower and upper walls are studied for Rayleigh numbers ranging from 10 3 to 10 5 and open aspect ratio varied from 0.0 to 0.8. The results show that the enhancement of the heat transfer is the greatest at high Rayleigh numbers and open aspect ratios. The best position for the open locations was found out to be on the upper wall as shown in case 3.

J23 ベーパーチャンバーの熱輸送特性に及ぼす熱源位置の影響(J2 熱工学2)

J23 ベーパーチャンバーの熱輸送特性に及ぼす熱源位置の影響(J2 熱工学2)

A numerical study on the influence of vulnerable plaque composition on intravascular thermography measurements

Intracoronary thermography is a technique that measures lumen wall temperatures for vulnerable plaque detection. In this paper the influence of vulnerable plaque composition on lumen wall temperatures was studied numerically. Concerning the vulnerable plaque heat generation, the location of the heat source and its heat production were varied. Concerning the heat transfer, the thermal properties of the lipid core and the location of the vasa vasorum were studied. The heat source location was the main determinant of the lumen wall temperature distribution. The strongest effect was noted when the heat producing macrophages were located in the shoulder region leading to focal spots of higher temperature. The maximal lumen wall temperature was mainly determined by the heat production of the macrophages and the cooling effect of blood. The insulating properties of the lipid core increased lumen wall temperatures when the heat source was located in the cap and the presence of vasa vasorum lowered the temperatures. These results show that the lumen wall temperature distribution is influenced by vulnerable plaque composition and that intracoronary thermography techniques require a high spatial resolution. To be able to couple temperature measurements to plaque vulnerability, intracoronary thermography needs to be combined with an imaging modality.

A study of the feasibility of using mathematical optimisation to minimise the temperature in a smelter pot room

Health hazards arise in large industrial workshops (such as aluminium pot rooms) due to the production of heat by the process equipment inside these workshops, which leads to high temperatures around these pieces of equipment. The heat production is sometimes accompanied by the release of polluting gases and dust particles that are dispersed throughout the workshop. The only large-scale and cost-effective way to ventilate these workshops is through natural ventilation. The effectiveness of the ventilation depends on the architectural shape of the building, the heat source locations and the openings of the windows, louvers and/or roof ventilators through which the air is allowed to enter and exit. This paper describes the investigation into the feasibility of using mathematical optimisation to determine the ideal window slat angles for different prevailing wind conditions. The proposed optimisation methodology employs computational fluid dynamics software (FLUENT), coupled to a computationally economic optimisation algorithm (Dynamic-Q) to determine the optimum slat angles to minimise the maximum temperature. The results of this feasibility study on a large-scale aluminium smelter pot room in Inota, Hungary, show that this is a viable methodology to determine the optimum inlet configuration.

Performance of Shrouded Pin-Fin Heat Sinks for Electronic Cooling

The objective of this study is to analyze the performance of a cylindrical pin-fin heat sink in laminar forced convection. The mathematical models are presented for predicting thermal and hydraulic resistances for both in-line and staggered arrangements. Analytical/empirical correlations of friction and heat transfer coefficients are used in the analysis. The analyses are performed by using parametric variation of resistances. The effects of thermal joint, spreading, and contact resistances as well as the thermal conductivity on the overall thermal performance are examined. For a given size and heat load, it is observed that the overall performance of a pin-fin heat sink depends on a number of parameters including the dimensions of the pin-fins, pin density, longitudinal and transverse spacings, interface material, location and size of heat sources, method of manufacturing, type of heat-sink material, approach velocity, and arrangement of pins. It is also observed that the thermal resistance decreases whereas pressure drop increases with an increase in approach velocity, pin diameter, and pin density. Nomenclature Ab = area of the base plate ≡ L × W ,m 2 Ac = cross-section or contact area of a single pin, m 2 Afin = surface area of a single pin, m 2 Ahs = surface area of heat sink, m 2 CV = control volume D = pin diameter, m f = friction factor H = pin height, m h = average heat transfer coefficient, W/m 2 · K he = uniform effective film coefficient, W/m 2 · K k = thermal conductivity, W/m · K ks = harmonic mean thermal conductivity for the two solids, W/m · K L = length of heat sink in flow direction, m m = fin performance parameter, m −1 N = total number of pins in heat sink ≡ NT NL NL = number of pins in the longitudinal direction NT = number of pins in the transverse direction Nu D = Nusselt number based on pin diameter ≡ Dh/k f P = contact pressure, N/m 2 Pr = Prandtl number ≡ ν/α Q = total heat transfer rate, W Rc = contact resistance between fins and the baseplate, K/W R f = total resistance of fluid side of heat sink, K/W Rfilm = thermal resistance of exposed (unfinned) surface of the baseplate, K/W Rfin = resistance of a fin, K/W R j = thermal joint resistance between the source and the baseplate, K/W Rm = material resistance of the baseplate, K/W Rs = thermal spreading resistance in the baseplate, K/W

A study of the effect of heat source location in a ventilated room using multiple regression analysis

Multiple regression analysis is a statistical technique which allows to predict a dependent variable from more than one independent variable and also to determine influential independent variables. Using experimental data, in this study the multiple regression analysis is applied to predict the room mean velocity and determine the most influencing parameters on the velocity. More than 120 experiments for four different heat source locations were carried out in a test chamber with a high level wall mounted air supply terminal at air change rates 3–6 ach. The influence of the environmental parameters such as supply air momentum, room heat load, Archimedes number and local temperature ratio, were examined by two methods: a simple regression analysis incorporated into scatter matrix plots and multiple stepwise regression analysis. It is concluded that, when a heat source is located along the jet centre line, the supply momentum mainly influences the room mean velocity regardless of the plume strength. However, when the heat source is located outside the jet region, the local temperature ratio (the inverse of the local heat removal effectiveness) is a major influencing parameter.

Natural convection heat transfer from a thermal heat source located in a vertical plate fin

A steady state conjugate conduction–convection investigation is performed on vertical plate fin in which a small heat source is located. Heat from the fin surface is transferred to the surroundings by laminar natural convection. The governing equations for the problem are the heat conduction equation for the fin and the boundary layer equations, which are continuity, momentum and energy equations, for the fluid. A computer program is written by using the finite difference method in order to solve the governing equations which are nonlinear and coupled. The best location of the heat source in the fin for maximum heat transfer rate depends on two parameters which are the conduction–convection parameter and the Prandtl number. The obtained results have shown that for the fin with large conduction–convection parameter, a heat source location for maximum heat transfer rate exists.

MIXED CONVECTION FROM ELECTRONIC EQUIPMENT COMPONENT AT DIFFERENT POSITION AN ENCLOUSER BY PRIMITIVE VARABILS METHOD

A numerical study of mixed convtion cooling of heat dissipating electronic component, located in a rectangular enclosure, and cooled by an external through flow of air is carried out.A conjugate problem is solved by primitive variables method, describing the flow and thermal fields in air .The interaction between the components is of interest here, depending on their relative placement in the enclosure, and different configuration are considered. for Re=100 laminar, steady flow is predicted for up to Gr/Re2 =25 according to heat source location in the enclosure. The mixed convection regime, where the buoyancy effects are comparable to the forced flow, occurs at values of Gr/Re2 between 0.01 and 25 .The results are of values in search for suitable placement of electronic components in an enclosed region for an effective heat removal. In general, it appears that the location of the source on the left vertical wall is the most favorable in terms of cooling. Laminar results are predicted up for up to Gr = 2.5*105 for all configurations studied

Optimal location of heat sources on a vertical wall with natural convection through genetic algorithms

Passive cooling of electronic components by natural convection heat transfer is the least expensive, quietest and most reliable method of heat rejection. However, some characteristics intrinsic to the phenomenon, such as a non-linear interaction between heat sources difficult its practical application. The objective of this work is to study the natural convection heat transfer optimization through genetic algorithms. Four cases were studied: one heat source, two heat sources with same dissipation rate, and two heat sources with different dissipation rates on a vertical wall. The results showed good agreement with literature and confirmed the methodology as computationally feasible for the optimal location of heat sources in a vertical wall.

Numerical procedure for predicting annual energy consumption of the under-floor air distribution system

As compared with the mixing system, indoor air temperature stratification in the under-floor air distribution (UFAD) system offers an opportunity for cooling load reduction in the occupied zone. This stratification is a major feature that offers the energy saving potential, but it has not been thoroughly taken into account in most energy simulation programs. In this article, a numerical procedure, based on coupling two types of modeling, i.e., CFD (computational fluid dynamic) simulation and dynamic cooling load simulation, is proposed to predict annual energy consumption. The dimensionless temperature coefficient is first defined in the UFAD system and obtained from CFD simulation, based on the boundary conditions from a cooling load program ACCURACY. According to this coefficient, temperature stratification input to ACCURACY is then revised to calculate the updated supply and exhaust air temperatures for final annual energy prediction. To demonstrate the method, a small office room is investigated using Hong Kong weather data. With the constant air volume (CAV) supply in the UFAD system, it is found that the dimensionless temperature coefficient is almost a constant, when the locations of heat sources are fixed. As compared with the mixing system, the UFAD system derives its energy saving potential from the following three factors: an extended free cooling time, a reduced ventilation load, and increased coefficients of performance (COP) for chillers.

Experimental investigation of mixed convection from an array of discrete heat sources at the bottom of a horizontal channel

Mixed convection heat transfer from an array of discrete heat sources inside a rectangular channel has been investigated experimentally under various operating conditions for air. The lower surface of the channel was equipped with 8 × 4 flush-mounted heat sources subjected to uniform heat flux, sidewalls and the upper wall are insulated and adiabatic. The experimental parametric study was made for an aspect ratio of AR = 10, Reynolds numbers 241 ≤ ReDh ≤ 980, and modified Grashof numbers Gr* = 9.53 × 105 to 1.53 × 107 . From the experimental measurements, surface temperature distributions of the discrete heat sources were obtained and effects of Reynolds and Grashof numbers on these temperatures were investigated. Furthermore, Nusselt number distributions were calculated for different Reynolds and Grashof numbers, with emphasis on changes obtained for different discrete heat source locations. From these results, the buoyancy affected secondary flow and the onset of instability have been discussed. Results show that surface temperatures increase with increasing Grashof number and decrease with increasing Reynolds number. However, with the increase in the buoyancy affected secondary flow and the onset of instability, temperatures level off and even drop as a result of heat transfer enhancement. This outcome can also be observed from the variation of the row-averaged Nusselt number showing an increase towards the exit, especially for low Reynolds numbers.

BUOYANCY-AIDED MIXED CONVECTION WITH CONDUCTION AND SURFACE RADIATION FROM A VERTICAL ELECTRONIC BOARD WITH A TRAVERSABLE DISCRETE HEAT SOURCE

This article presents the results of a comprehensive fundamental numerical study of the problem of buoyancy-aided mixed convection with conduction and surface radiation from a vertical electronic board provided with a traversable, flush-mounted, discrete heat source. Air, a radiatively transparent medium, is considered to be the cooling agent. The governing equations in primitive variables for fluid flow and heat transfer are first converted into stream function–vorticity form, and are later converted into algebraic form using the finite-volume method. The resulting finite-difference equations are solved by Gauss-Seidel iterative technique. The governing equation for temperature distribution along the electronic board is obtained by appropriate energy balance. The effects of pertinent parameters, viz., location of the discrete heat source, surface emissivity of the board, and modifiedRichardson number, on various results, including local temperature distribution along the board, maximum board temperature, and contributions of convection and surface radiation to heat dissipation from the board, are studied in great detail. The fact that any design calculation that ignores surface radiation in problems of this kind would be error-prone is clearly highlighted.

Numerical Identification Of A Source Location InSteady State Heat Conduction

An identification problem is considered for detecting the location of a single heat source in a body in the steady state of heat conduction. The detection is based on the partial observation of temperatures and heat fluxes on part of the surface. The boundary element method and high order finite difference method are used for a computational tool with the benefit of their high accuracy. Numerical results are presented to show the usefulness of the proposed method for identification.

Natural Convection and Passive Heat Rejection from Two Heat Sources Maintained at Different Temperatures on a Printed Circuit Board

Natural convection and passive heat rejection from two independent heat sources maintained at different temperatures (60°C and 100°C above ambient) on single circuit boards (FR4 and copper clad FR4) are experimentally studied. The effect of heat source location on maximum power dissipation is presented for both horizontal and vertical orientations. Heat losses due to radiation, natural convection and board conduction are quantified. As long as the heat sources are more than 2 cm apart, they do not influence each other on the FR4 board. Vertical orientation increases the power dissipation in the components by up to 30% for the FR4 board and 15% for the copper clad board. Two ounces of copper cladding increases the overall power dissipation by 150–190%.

Design of boilers with catalytic fluidised bed and their connection to heat supply system

The new advantage of catalytic boiler consisting of the location of heat source near the consumer is described. It imposes some restrictions on the design of such a boiler, which is based on the zonal arrangement approach. The details of such design of boilers with catalytic fluidised bed intended for different purposes (water heating, steam generation, steam superheating) are considered and, in particular, for the boiler with heat capacity 2MW. The description of all main boiler elements is given. There are also the details of working of the autonomous catalytic boiler with fluidised bed in the system of heat and hot water supply.

A parameter estimation approach to solve the inverse problem of point heat sources identification

This paper deals with an inverse problem that consists of the identification of multiple line heat sources placed in a homogeneous domain. In the inverse problem under investigation the location and strength of the line heat sources are unknown. The estimation procedure is based on the boundary element method. As the discrete problem is non-linear if the location of the line heat sources is unknown, an iterative procedure has to be applied to find out the location of the sources. The proposed approach has been tested for steady and transient experiments. In the present study we propose an original approach to solve the steady problem. As in the steady heat conduction case we have a limited number of unknown for each source, a “parameter estimation” approach can be applied to estimate the sources. Using the techniques of parameter estimation, we can also estimate the confidence interval of the estimated locations, which permits to design an optimal experiment. We intend to present some numerical and experimental 2D results.

Velocity structure and a seismic model for Nevado del Ruiz Volcano (Colombia)

A seismic tomographic study was performed for Nevado del Ruiz Volcano (NRV) using more than 1500 high-quality local and regional. Three low P wave velocity (low- V P) and low S wave velocity (low- V S) zones were found; one low- V S zone at depths 2–4 km located beneath the volcano; a second low- V P and low- V S zone at depths 5–10 km located beneath the crater, elongated and dipping to the E–SE; and a third low- V P and low- V S zone at 10 to ∼12 km farther to the east. These three low- V P and low- V S zones are believed to be the location of heat sources. A high-velocity zone for both P and S waves was found at shallow depths (0∼5 km) around the active crater. The upper part (0∼2 km depth) of the high- V P and high- V S zone was characterized by low- V P/ V S ratios (<1.68), while the deeper part (2∼10 km) had high- V P/ V S ratios (>1.80). The low- V P/ V S zone is correlated with a steam-dominated geothermal system. The high- V P/ V S is interpreted as an intrusive body of magmatic origin which includes partial melting zones associated with low- V S anomalies. A small low- V P zone in which long-period (LP) earthquakes were clustered was found to the southwest of the volcano. Based on the data obtained with the tomography in combination with seismicity, geochemistry, geology and gravimetry, we suggest a model for the seismic activity of NRV. Volcano-tectonic (VT) earthquakes that occur very often in swarm-like patterns located in several clusters around the volcano seem to be due to changes in stress produced by the passing of fluids and/or gas through many small cracks. A fault and a caldera-like structure separate the VT swarms located to the west of the volcano from the source of LP earthquakes.