scholarly journals Thermoradial drying of paper coatings

2005 ◽  
Vol 59 (7-8) ◽  
pp. 190-193
Author(s):  
Vladimir Valent
Keyword(s):  
Heat Flux ◽  
Solid Phase ◽  
Optical Characteristics ◽  
Technical Solution ◽  
Paper Coatings ◽  
Large Heat

The thermoradial drying of material (paper) was discussed. The basic and most important parameters of the process of industrial drying were defined. Thermoradial drying provides a relatively large heat flux to the wetted material. It shortens the time of drying and is advantageous for drying liquid coatings on the surface of the paper. The technical solution of the iradiation method must be defined taking into account the structural absorptive and optical characteristics of the formed solid phase of the coating.

The Temperature Distribution Within a Sphere Placed in a Directed Uniform Heat Flux and Allowed to Radiatively Cool

1985 ◽  
Vol 107 (1) ◽  
pp. 28-32 ◽  
Author(s):  
D. Duffy
Keyword(s):  
Heat Flux ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Analytic Solution ◽  
Blackbody Radiation ◽  
Heat Fluxes ◽  
Uniform Heat Flux ◽  
Transform Methods ◽  
Uniform Heat ◽  
Large Heat

The temperature field within a sphere is found when the sphere is heated by a directed heat flux and cooled by blackbody radiation. For small heat fluxes, the analytic solution is obtained by transform methods. For large heat fluxes, the solution is computed numerically.

scholarly journals Improvement of operation of steam cushion system for sensible thermal energy storage

2019 ◽  
Vol 116 ◽  
pp. 00107
Author(s):  
Ryszard Zwierzchowski
Keyword(s):  
Heat Flux ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Energy Savings ◽  
Operating Conditions ◽  
Production Costs ◽  
Technical Solution ◽  
Atmospheric Air ◽  
Suction Pipe

The paper contains a method for improvement of operation of steam cushion system including its energy savings analyses, for a Thermal Energy Storage (TES) tank. Energy savings analyses were performed using operational data from selected Combined Heat and Power plants, which supply heat to large cities in Poland and are furnished with the TES. The role of the steam cushion system in the TES tank is to prevent the stored water against absorbing oxygen from atmospheric air. In the TES tank, which is a non-pressure tank, oxygen from atmospheric air could penetrate to the network water through the surge chamber and safety valves. The steam pressure under the roof is generated from technological steam injected under the roof. Energy savings in the steam cushion system are generated by using an appropriate technical solution for the upper orifice and suction pipe for circulation water, i.e., to make it movable through the use of pontoons. An isolating buffer layer is created at the top of the tank with very small convective and turbulent heat transport, which causes limited heat transfer from steam bed to the stored water in the tank. This results in heat flux of approximately 10% of the heat flux that occurs in the typical technical solution of the upper orifice and suction pipe for circulation water in the TES tank. This technology offers great opportunities to improve the operating conditions of District Heating System, cutting energy production costs and emissions of pollutants to the atmosphere.

Application of Film Dryout Model in Liquid Metal CHF Prediction

2014 ◽  
Author(s):  
Zaiyong Ma ◽  
Yue Nina ◽  
Suizheng Qiu ◽  
Wenxi Tian ◽  
Guanghui Su
Keyword(s):  
Heat Flux ◽  
Liquid Metal ◽  
Deposition Rate ◽  
Annular Flow ◽  
Nuclear Reactors ◽  
Liquid Metals ◽  
Large Error ◽  
Entrainment Rate ◽  
Large Heat ◽  
Sodium And Potassium

Liquid metals have been used as coolants of several kinds of nuclear reactors, and the prediction of critical heat flux (CHF) is rather important for the design, safety and economy of these reactors. A film dryout model considering the deposition and entrainment of droplets was established to obtain the CHF of liquid metal in annular flow flowing in tubes. The correlations of deposition rate, entrainment rate and so on for conventional fluids were used, and the initial entrainment fraction was determined according to experimental data. Results showed that the correlations for conventional fluids could be used for liquid metals approximately, but relatively large error might occur for large heat flux. The accuracy of this model for sodium and potassium was similar for small heat flux, but had some differences for large heat flux. Special correlations of deposition rate, entrainment rate and so on should be developed to predict the CHF of liquid metals more accurately.

Numerical Investigation of Thermofluid Flow Characteristics With Phase Change Against High Heat Flux in Porous Media

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Kazuhisa Yuki ◽  
Jun Abei ◽  
Hidetoshi Hashizume ◽  
Saburo Toda
Keyword(s):  
Heat Flux ◽  
Solid Phase ◽  
Flow Characteristics ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Two Phase ◽  
Thermal Nonequilibrium ◽  
Phase Mixture ◽  
Flow Case

This study numerically evaluates thermofluid flow characteristics in porous medium by a newly developed “modified two-phase mixture model” applying Ergun’s law and a two-energy model instead of a one-energy model. In a single-phase flow case, thermal nonequilibrium between a solid phase and a fluid phase is observed in the area where imposed heat conducts from a heating wall and further convective heat transfer is more active. The degree of thermal nonequilibrium has a positive correlation with the increase in flow velocity and heat flux input. In the case of two-phase flow, the thermal nonequilibrium is remarkable in the two-phase region because the solid-phase temperature in this region is far beyond saturation temperature. A difference between these two models is obvious especially in the two-phase flow case, so that the numerical simulation with the modified two-phase mixture model is indispensable under the high heat flux conditions of over 1MW∕m2.

scholarly journals Giant heat transfer in the crossover regime between conduction and radiation

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Konstantin Kloppstech ◽  
Nils Könne ◽  
Svend-Age Biehs ◽  
Alejandro W. Rodriguez ◽  
Ludwig Worbes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Near Field ◽  
Black Body ◽  
Black Body Radiation ◽  
Quantitative Measurements ◽  
Atomic Spacing ◽  
Large Heat ◽  
Vacuum Gaps ◽  
Near Field Scanning

Abstract Heat is transferred by radiation between two well-separated bodies at temperatures of finite difference in vacuum. At large distances the heat transfer can be described by black body radiation, at shorter distances evanescent modes start to contribute, and at separations comparable to inter-atomic spacing the transition to heat conduction should take place. We report on quantitative measurements of the near-field mediated heat flux between a gold coated near-field scanning thermal microscope tip and a planar gold sample at nanometre distances of 0.2–7 nm. We find an extraordinary large heat flux which is more than five orders of magnitude larger than black body radiation and four orders of magnitude larger than the values predicted by conventional theory of fluctuational electrodynamics. Different theories of phonon tunnelling are not able to describe the observations in a satisfactory way. The findings demand modified or even new models of heat transfer across vacuum gaps at nanometre distances.

Heat Transfer Characterizations of Heat Pipe in Comparison With Copper Pipe

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Chen-Ching Ting ◽  
Jing-Nang Lee ◽  
Chien-Chih Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Source ◽  
Heat Pipe ◽  
Heat Conductivity ◽  
Cooling Efficiency ◽  
Copper Pipe ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Large Heat

The article presents some significant experimental data for studying the heat transfer behavior of heat pipe, which will further help the cooling efficiency improvement of the heat pipe cooler. It is well known that the heat pipe owns the extreme large heat conductivity and is often integrated with cooling plates for CPU cooling. The heat pipe uses special heat transfer techniques to obtain extremely large heat conductivity, which are the inside liquid evaporation for heat absorption and the inside microstructural capillarity for condensation. These special techniques yield the instant heat transfer from the heat source to the remote side directly, but the special heat transfer behavior is changed due to the integration with cooling plates. The destroyed heat transfer behavior of the heat pipe causes the cooling efficiency of the heat pipe cooler to be not able to reach a predicted good value. To improve the cooling efficiency of the heat pipe cooler we recover the original heat transfer behavior of the heat pipe integrated with cooling plates. This work first built a CPU simulator in accordance with the ASTM standard for heating the heat pipe, then uses the color schlieren technique to visualize the sequent heat flux nearby the heat pipe and the infrared thermal camera for quantitative temperature measurements synchronously. The result shows that the heat flux first appears at the opposite side from the heat source and there exhibits also the highest temperature. This is different from the heat transfer behavior of the copper pipe. Another very interesting result is that the heat flux of the cooling plate nearest to the heat source is first viewed than the others, which is similar to the integration with the copper pipe.

Anomalous dissipation nearTλunder a large heat flux

1998 ◽  
Vol 57 (1) ◽  
pp. 536-541 ◽  
Author(s):  
Daniel Murphy ◽  
Horst Meyer
Keyword(s):  
Heat Flux ◽  
Large Heat ◽  
Anomalous Dissipation

Large Heat Transport Due to Spontaneous Gas Oscillation Induced in a Tube With Steep Temperature Gradients

1983 ◽  
Vol 105 (4) ◽  
pp. 889-894 ◽  
Author(s):  
T. Yazaki ◽  
A. Tominaga ◽  
Y. Narahara
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Helium ◽  
Heat Conductivity ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Large Heat

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

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