Heat Flow Calorimetry

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Flow ◽  
Heat Sink ◽  
Reaction Vessel ◽  
Heat Output ◽  
Large Numbers ◽  
Different Temperatures

Heat flow calorimeters, also known as “heat flux,” “heat conduction,” or “heat leakage” calorimeters, are instruments where the heat output or input associated with a given phenomenon is transferred between a reaction vessel and a heat sink. This heat transfer can be monitored with high thermal conductivity thermopiles containing large numbers of identical thermocouple junctions regularly arranged around the reaction vessel (the cell) and connecting its outside wall to the heat sink (the thermostat). The determination of the heat flow relies on the so-called Seebeck effect. An electric potential, known as thermoelectric force and represented by E, is observed when two wires of different metals are joined at both ends and these junctions are subjected to different temperatures, T1 and T2. Several thermocouples can be associated, forming a thermopile. For small temperature differences, the thermoelectric force generated by the thermopile is proportional to T1 − T2 and to the number of thermocouples of the pile (n): E = nε ′ (T1 − T2) (9.1) where ε′ is the thermoelectric power of a single thermocouple (ε′ = dE/dT).

scholarly journals Study of Thermal Performance of Closed Loop Pulsating Heat Pipe using Computational Fluid Dynamics

2021 ◽  
Vol 9 (9) ◽  
pp. 1384-1388
Author(s):  
K. C. Giri
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Different Temperatures

Abstract: Pulsating heat pipe is a heat transfer device which works on two principles that is phase transition and thermal conductivity which transfer heat effectively at different temperatures. Different factors affect the thermal performance of pulsating heat pipe. So, various researchers tried to enhance thermal conductivity by changing parameters such as working fluids, filling ratio, etc. Analysis of heat transfer characteristics of closed loop pulsating heat pipe (CLPHP) is to be carried out by using Computational Fluid Dynamics. The CLPHP is to be modelled on ANSYS Workbench, the flow of CLPHP is to be observed under specific boundary conditions by using ANSYS Fluent software. Acetone and Water are taken as the working fluid with 70% filling ratio at ambient temperature 30° C and the heat flux of 200 W is supplied at evaporator. Also, the analysis has been done to know the behaviour of PHPs under varying supply of heat flux at evaporator (inlet), the output heat flux is obtained at condenser (outlet) and find out how the heat flux is varying at different temperatures. CFD results shows the heat transfer characteristics observing the performance of CLPHP is a numerical manner. The obtained CFD results are compared with the experimental. The outputs of the simulations are plotted in graphs and outlines. Keywords: Closed Loop Pulsating Heat Pipe, CFD, Heat Transfer, ANSYS.

Determination of the Thermal Constants of the Heat Flow Equations of Electrical Machines

1969 ◽  
Vol 184 (9) ◽  
pp. 84-92 ◽  
Author(s):  
T. J. Roberts
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Sheet Steel ◽  
Electrical Machine ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Heat Transfer Coefficients ◽  
Thermal Constants

One of the major problems in obtaining accurate predictions of temperature distribution within an electrical machine is the values of the thermal constants used in the solution of the heat flow equations. A line source method is developed for anisotropic materials and is used to determine the thermal conductivity of sheet steel laminations. Results are given for three typical sheet steels showing the effect of varying core clamping pressure. The thermal conductivity of high-voltage insulation is obtained from tests on production machine coils and values are given for typical insulation systems. A model test is described for the evaluation of the heat transfer coefficients from the cooling surfaces of the radial air ducts, based on the assumption of a uniform distribution of air across the duct entrance. The heat transfer coefficients from the other cooled surfaces within the machine are determined from full-scale temperature measurements on production machines. The limitation of this latter method of determination of heat transfer coefficient is evaluated.

scholarly journals A Miniaturized 3D Heat Flux Sensor to Characterize Heat Transfer in Regolith of Planets and Small Bodies

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4135
Author(s):  
Manuel Domínguez-Pumar ◽  
Jose-Antonio Rodríguez-Manfredi ◽  
Vicente Jiménez ◽  
Sandra Bermejo ◽  
Joan Pons-Nin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Flow ◽  
Thermal Environment ◽  
Heat Flux Sensor ◽  
Flux Vector ◽  
Small Bodies ◽  
Heat Flux Vector ◽  
Flux Sensor

The objective of this work is to present the first analytical and experimental results obtained with a 3D heat flux sensor for planetary regolith. The proposed structure, a sphere divided in four sectors, is sensible to heat flow magnitude and angle. Each sector includes a platinum resistor that is used both to sense its temperature and provide heating power. By operating the sectors at constant temperature, the sensor gives a response that is proportional to the heat flux vector in the regolith. The response of the sensor is therefore independent of the thermal conductivity of the regolith. A complete analytical solution of the response of the sensor is presented. The sensor may be used to provide information on the instantaneous local thermal environment surrounding a lander in planetary exploration or in small bodies like asteroids. To the best knowledge of the authors, this is the first sensor capable of measuring local 3D heat flux.

The influence of some design parameters on the heat transfer in thermal fuel flowmeter

2021 ◽  
Vol 13 (1) ◽  
pp. 54-59
Author(s):  
Andriy Ilchenko ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Flow ◽  
Fuel Consumption ◽  
Design Parameters ◽  
Radial Heat Flow ◽  
Radial Heat ◽  
Axial Heat ◽  
Radial Heat Flux

The article analyzes the influence, relationship and value of design parameters of the heat flow meter on its radial and axial heat fluxes in the tube (tube diameter, heater diameter and their ratio, thermal conductivity of the tube material, etc.). It is shown that at the stage of choosing the design parameters of the flowmeter it is necessary to take into account the influence of its radial heat flux on the axial one. The influence of radial heat flux in the flowmeter tube on the error of fuel loss measurement is substantiated. Analytical dependences which allow to define an axial heat stream are resulted, their analysis concerning influence of flowmeter tube constructive parameters on heat transfer is carried out. Measures are planned and recommendations are developed for the choice of design flowmeter parameters, development or use, provided that the influence of radial heat flow on the axial is reduced, which will reduce the total error of fuel consumption measurement. Regarding the choice of design parameters of heat meters while reducing the error of measuring fuel consumption, it is shown that the maximum possible decrease in the diameter of the heater and increase the diameter of the flow tube reduce the impact of radial heat flow on the axial and thus reduce the total fuel consumption error. Numerical ratios of tube diameter to flowmeter heater diameter for different thermal conductivities of tube materials are given under the condition of minimal influence on fuel consumption measurement error. For tube materials with a thermal conductivity 0.16… 0.25 W / (m ∙ K) (ebonite, fluoroplastic F-5, etc.) the tube diameters ratio and the heater should be within 1.51… 1.62, and for materials with more high thermal conductivity (thermal conductivity greater than 14.9 W / (m ∙ K)), this ratio should be equal to 1.99.

scholarly journals Thermal conductivity of sandstones from Biot’s coefficient

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. D173-D185 ◽  
Author(s):  
Tobias Orlander ◽  
Eirini Adamopoulou ◽  
Janus Jerver Asmussen ◽  
Adam Andrzej Marczyński ◽  
Harald Milsch ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Cross Section ◽  
Geometric Mean ◽  
Well Log ◽  
Biot’S Coefficient ◽  
Model Predictions ◽  
The Cross ◽  
Rock Texture

Thermal conductivity of rocks is typically measured on core samples and cannot be directly measured from logs. We have developed a method to estimate thermal conductivity from logging data, where the key parameter is rock elasticity. This will be relevant for the subsurface industry. Present models for thermal conductivity are typically based primarily on porosity and are limited by inherent constraints and inadequate characterization of the rock texture and can therefore be inaccurate. Provided known or estimated mineralogy, we have developed a theoretical model for prediction of thermal conductivity with application to sandstones. Input parameters are derived from standard logging campaigns through conventional log interpretation. The model is formulated from a simplified rock cube enclosed in a unit volume, where a 1D heat flow passes through constituents in three parallel heat paths: solid, fluid, and solid-fluid in series. The cross section of each path perpendicular to the heat flow represents the rock texture: (1) The cross section with heat transfer through the solid alone is limited by grain contacts, and it is equal to the area governing the material stiffness and quantified through Biot’s coefficient. (2) The cross section with heat transfer through the fluid alone is equal to the area governing fluid flow in the same direction and quantified by a factor analogous to Kozeny’s factor for permeability. (3) The residual cross section involves the residual constituents in the solid-fluid heat path. By using laboratory data for outcrop sandstones and well-log data from a Triassic sandstone formation in Denmark, we compared measured thermal conductivity with our model predictions as well as to the more conventional porosity-based geometric mean. For outcrop material, we find good agreement with model predictions from our work and with the geometric mean, whereas when using well-log data, our model predictions indicate better agreement.

scholarly journals INSTALLATION FOR DETERMINATION OF HEAT RELEASE OF HEATING RADIATORS

2021 ◽  
Vol 4 (164) ◽  
pp. 77-81
Author(s):  
Yu. Ivashina ◽  
V. Zavodyannyi
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Electrical Power ◽  
Electric Heating ◽  
Middle Part ◽  
Heat Losses ◽  
The Body ◽  
Heat Output ◽  
Stationary Mode

To calculate the share of thermal energy consumed by this apartment in an apartment building, it is necessary to determine the heat transfer of all heating radiators in the house. But the heat transfer given in the passport of the heating device corresponds to the temperature pressure equal to 70K. Often the owners install non-standard devices, so the problem of determining the heat transfer of heating radiators in real conditions is relevant. Thermometric method, which is called electric, is widely used for laboratory determination of heat transfer of heating devices. Water by means of the pump circulates through an electric copper and the investigated radiator. The heat output of the latter is defined as the difference between the supplied electrical power (boiler power plus pump) and heat loss. The purpose of the work is to develop and study the operation of the installation for determining the heat transfer of heating radiators, which had a simpler design and could ensure proper measurement accuracy. We have proposed a scheme and design of the installation for determining the heat transfer of electric heating radiators, which differs in that it does not include a circulating pump. Water in the system circulates under the action of gravity due to changes in the density of the coolant during heating and cooling. This greatly simplifies the circuit by eliminating not only the pump but also the valve and the air outlet valve. The heater chamber is made of a steel pipe with a diameter of 88 mm. A steel cover is attached to the lower flange, through which a 1-1.5 kW heater is introduced into the chamber. Two 1/2 ″ sections of pipe are welded to the body of the heater chamber, through which the radiator is connected by means of rubber couplings. The cylindrical surface of the chamber on top of the layer of internal insulation is covered with a shielding heater, the temperature of which is maintained equal to the surface temperature of the heater chamber in the middle part. A layer of external thermal insulation is installed on top of the shielding heater. To determine heat loss, the radiator is disconnected from the heater chamber, plugs are installed and insulated. In stationary mode, the dependence of the heater power on the temperature of the heater chamber is measured, which determines the power of heat losses. The simplification of the installation has led not only to its reduction in price, but also to an increase in accuracy due to the reduction of heat losses and the simplicity of their definition.

Interfacial instabilities in plane Poiseuille flow of two stratified viscoelastic fluids with heat transfer. Part 1. Evolution equation and stability analysis

1995 ◽  
Vol 299 ◽  
pp. 241-265 ◽  
Author(s):  
Sang W. Joo
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Stability Analysis ◽  
Evolution Equation ◽  
Vertical Channel ◽  
Viscoelastic Fluids ◽  
Lubrication Approximation ◽  
Plane Poiseuille Flow ◽  
Interfacial Instabilities ◽  
Different Temperatures

An evolution equation is derived that describes the nonlinear development of the interface between two viscoelastic fluids flowing, under the action of imposed pressure gradient and gravity, in a vertical channel. The channel walls are kept at different temperatures, resulting in heat transfer across the layers. The equation, based on the lubrication approximation, models the effects of stratifications in density, viscosity, elasticity, shear thinning, and thermal conductivity. It also describes the capillary and thermocapillary effects, as well as the sensitivity of viscosities to temperature. Linear-stability analysis is performed based on the evolution equation to understand the competing effects of viscous, elastic, and Marangoni instabilities. Particular attention is paid to the active control of the interfacial instabilities through the thermocapillarity.

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