scholarly journals Thermal Properties of Systems Exhibiting Optimum Countercurrent Heat Exchange

1964 ◽  
Vol 17 (1) ◽  
pp. 26 ◽  
Author(s):  
RCL Bosworth ◽  
CM Groden
Keyword(s):  
Thermal Properties ◽  
Heat Exchange ◽  
Heat Flow ◽  
Temperature Difference ◽  
Linear Dimension ◽  
Constant Pressure ◽  
Mechanical Work ◽  
Pivotal Point ◽  
Specific Heats ◽  
Pass Through

Heat flow in heat exchange systems, operating at constant pressure, is.considered in relation to the thermodynamical measure of entropy called by Keenan. the availability. The ratio of the maximum attainable mechanical work from two.systems (1) and (2) is shown to be equal to the ratio of the two availabilities or.l:1B1/l:1Bg, and this reasonably approaches unity only when the exchanger involves.countercurrent flow. The temperatures and temperature differences may be plotted against the linear dimension along the exchanger. The temperature difference will pass through one or more stationary values associated with a temperature T*. At such a pivotal point, we may define enthalpies, l:1H;, l:1H; and specific heats (c;, c;) of the two streams in which the following relations hold:

scholarly journals The effect of pressure upon natural convection in air

1936 ◽  
Vol 157 (891) ◽  
pp. 278-291 ◽  
Keyword(s):  
Natural Convection ◽  
Heat Flow ◽  
Specific Heat ◽  
Linear Dimension ◽  
Constant Pressure ◽  
Unit Area ◽  
Dimensionless Numbers ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Made In

Dimensional considerations show, on certain assumptions, that natural convection depends upon the dimensionless numbers M = ag θ l 3 sρ 2 / μk , and N, = μ s / k , where l is a representative linear dimension, θ a representative temperature difference, a the coefficient of expansion of the fluid, s the specific heat per unit mass at constant pressure, ρ the density, μ the viscosity, and k the conductivity. If H denotes the rate of heat flow across unit area of any given surface within the fluid, it also follows that P, = H l / k θ, is a function of M and N. The assumptions made are discussed in an Appendix. For gases N varies little between wide limits of pressure and temperature, and may in general be omitted, P therefore depending only upon M. For a given gas, M is proportional to θ l 3 , and increases with the pressure p , being nearly proportional to p 2 . The variation of P with M can be found by experiments in which either θ, l , or p is varied, but the range of M to be got by varying θ is relatively small, not only because of the different indices in M, but also because for large values of θ the assumption made in the dimensional analysis, that the constants of the gas do not vary with temperature, is inadmissible. By varying the pressure, M can be varied over a wide range for a single value of l ; thus only one experimental apparatus need be constructed, and it may be of reasonable size, large surfaces being difficult to heat uniformly and the surrounding conditions difficult to control.

scholarly journals A flow method for comparing the specific heats of gases. part II.—The theory of the method

1930 ◽  
Vol 126 (801) ◽  
pp. 333-354 ◽  
Keyword(s):  
Electric Current ◽  
Temperature Difference ◽  
Constant Pressure ◽  
Flow Speed ◽  
Simple Method ◽  
Narrow Tube ◽  
Flow Method ◽  
Specific Heats ◽  
Cubic Equation ◽  
Experimental Values

In Part I a description was given of a simple method for the direct com­parison of the specific heats of gases at constant pressure. A particular form of the method consists in keeping the two ends of a narrow tube at the same temperature and heating the central portion by means of an electric current. Thermo-junctions are attached to the tube at two positions symmetrical about the centre of the tube, so that the junctions are initially at the same temperature. On passing a gas at a known speed through the tube a temperature difference between the two junctions is established, and this temperature difference was shown to be related to the flow speed by a cubic equation of the form:― Θ = C 1 α + C 3 α 3 (8) where α = σq / 2KA. In this paper it is proposed to investigate the theory of the method in detail, in order to prove the validity of the form of (8), and to evaluate the coefficients C 1 and C 3 so as to compare them with the experimental values given in Part I.

MODELING THE EFFECT OF HEAT EXCHANGE ON THE EFFICIENCY OF A THERMOELECTRIC COOLER

2020 ◽  
Vol 2 ◽  
pp. 132-135
Author(s):  
O.I. MARKOV
Keyword(s):  
Numerical Calculation ◽  
Heat Exchange ◽  
Solid State ◽  
Numerical Modelling ◽  
Temperature Difference ◽  
Maximum Temperature ◽  
Thermoelectric Cooler ◽  
Maximum Temperature Difference ◽  
Peltier Cooler ◽  
Account Heat

Numerical modelling thermal and thermoelectric processes in a branch of solid–state thermoelectric of Peltier cooler is performed, taking into account heat exchange by convection and radiation. The numerical calculation of the branch was carried out in the mode of the maximum temperature difference.

Estimation of the thermal properties of hardened cement paste on the basis of guarded heat flow meter measurements

2014 ◽  
Vol 588 ◽  
pp. 1-10 ◽  
Author(s):  
Seyoon Yoon ◽  
Donald E. Macphee ◽  
Mohammed S. Imbabi
Keyword(s):  
Thermal Properties ◽  
Heat Flow ◽  
Cement Paste ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Flow Meter ◽  
Heat Flow Meter ◽  
Guarded Heat Flow Meter

Thermal properties of fats and oils. VIII. Specific heats, heats of fusion, and entropy of alpha and beta tung oils

1952 ◽  
Vol 29 (4) ◽  
pp. 155-157 ◽  
Author(s):  
T. L. Ward ◽  
W. S. Singleton ◽  
R. W. Planck
Keyword(s):  
Thermal Properties ◽  
Fats And Oils ◽  
Specific Heats

scholarly journals Human Machine and Thermoelectric Energy Scavenging for Wearable Devices

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Vladimir Leonov
Keyword(s):  
Thermal Properties ◽  
Heat Flow ◽  
Thermal Resistance ◽  
Wearable Devices ◽  
The Body ◽  
Energy Scavenging ◽  
Wearable Electronics ◽  
Ambient Temperatures ◽  
Thermoelectric Energy ◽  
Temperature Heat

Thermal properties of humans were studied in the case where a small-size energy scavenger is placed on the body. In such a case, the human being serves as a heat source for the thermopile of the scavenger, but the latter serves as a thermally insulating object. As a result, the body properties, namely, the skin temperature, heat flow, and thermal resistance locally change. This is the result of redirection of heat flow inside the body to colder zones because of thermal insulation provided by the scavenger. Increased thermal resistance of human body, in turn, affects the design of the scavenger. The analysis of such scavenger performed for ambient temperatures of 0°C to 25°C shows that it could reach competitive performance characteristics and replace batteries in low-power wearable electronics. A simulated power of up to 60 μW/cm2 at 0°C has been validated by using wearable thermoelectric modules.

High Temperature and High Pressure ESP Performance Testing System Design

2013 ◽  
Vol 457-458 ◽  
pp. 423-427
Author(s):  
Xiao Qing Li ◽  
Xiao Yan Liu
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Heat Exchange ◽  
Liquid State ◽  
Constant Pressure ◽  
Hot Water ◽  
Testing System ◽  
Friction Resistance ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

With the development of oilfield exploration, the performance of electric submersible pump (ESP) has been enhanced very fast. It requires testing techniques develop at the same time. The most outstanding question is the testing of high temperature and pressure ESP. A testing well was drilled in Daqing in 1992. It keeps the water liquid state on 150 centigrade by high pressure. This system can simulate operational mode 3000 meters under the ground. But many new ESPs have been produced these years. The quondam testing system couldnt meet the testing requirement. A new testing system is desiderated eagerly. This paper developed a high temperature and pressure ESP testing experimentation system. Hydraulic/thermodynamic analysis calculation has been carried on. Friction resistance from constant pressure point to the suction inlet of hot water pump and the ESP in heating-forced cycle and experimentation primary cycle are calculated respectively. Keeping the water liquid state on 180 centigrade, constant pressure value was fixed on 2.5 MPa. The heat load is calculated including the heat that the water in the system and the equipment need and the heat loss. In order to protect ESP from emanating too much heat to keep the temperature and pressure of the system steady, heat exchange system has been designed. Cold load and heat exchange square have been calculated. Friction resistance and the size of the cold water cistern have been calculated. These provide necessary academic foundation for the testing experimentation of high temperature and pressure ESP.

scholarly journals I. On the ratio of the specific heats of the paraffins, and their monohalogen derivatives

1894 ◽  
Vol 185 ◽  
pp. 1-36 ◽  
Keyword(s):  
Thermal Properties ◽  
Kinetic Theory ◽  
Kinetic Theory Of Gases ◽  
Perfect Gas ◽  
Specific Heats ◽  
Different Gases

The experiments to be described in the present paper were undertaken in the hope of obtaining data which would throw light on one of the most obscure points of the kinetic theory of gases, namely, the distribution of energy in the molecule. The properties of gases on which the kinetic theory gained its reputation were the constancy of the product of pressure and volume, and the uniformity of the coefficient of expansion. For the explanation of these in the ease of the hypothetical perfect gas no knowledge of the special constitution of the molecule is required, but for most other properties, and especially thermal properties, the kinetic theory fails to explain the facts from want of information concerning the dynamical peculiarities of the molecules of different gases.

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