scholarly journals THERMOPHYSICAL PROPERTIES OF POLYMER MICROAND NANOCOMPOSITES BASED ON POLYCARBONATE

2015 ◽  
Vol 37 (2) ◽  
pp. 12-19
Author(s):  
A. A. Dolinskiy ◽  
N. M. Fialko ◽  
R. V. Dinzhos ◽  
R. A. Navrodskaya
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Thermophysical Properties ◽  
Percolation Theory ◽  
Heat Exchangers ◽  
Experimental Studies ◽  
Low Grade ◽  
Thermophysical Characteristics ◽  
Hostile Environments ◽  
Low Grade Heat

The results of experimental studies by the performed complex of thermophysical characteristics of created polymeric microand polycarbonate-based nanocomposites, which comprise from 0.2 to 10% carbon nanotubes and microparticles of aluminum are presented. Materials on the interpretation of the data based on the percolation theory are submitted. The possibilities of using of offered composites for the production of heat exchangers, focused on low-grade heat transfer and operating in hostile environments are previewed.  

scholarly journals Ground-Coupled Natural Circulating Devices (Thermosiphons): A Review of Modeling, Experimental and Development Studies

Inventions ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 14
Author(s):  
Messaoud Badache ◽  
Zine Aidoun ◽  
Parham Eslami-Nejad ◽  
Daniela Blessent
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Low Temperatures ◽  
Experimental Studies ◽  
Heat Transfer Fluid ◽  
Fluid Circulation ◽  
Ground Heat Exchangers ◽  
Additional Equipment ◽  
Different Types ◽  
Overall Efficiency

Compared to conventional ground heat exchangers that require a separate pump or othermechanical devices to circulate the heat transfer fluid, ground coupled thermosiphons or naturallycirculating ground heat exchangers do not require additional equipment for fluid circulation in theloop. This might lead to a better overall efficiency and much simpler operation. This paper providesa review of the current published literature on the different types of existing ground coupledthermosiphons for use in applications requiring moderate and low temperatures. Effort has beenfocused on their classification according to type, configurations, major designs, and chronologicalyear of apparition. Important technological findings and characteristics are provided in summarytables. Advances are identified in terms of the latest device developments and innovative conceptsof thermosiphon technology used for the heat transfer to and from the soil. Applications arepresented in a novel, well-defined classification in which major ground coupled thermosiphonapplications are categorized in terms of medium and low temperature technologies. Finally,performance evaluation is meticulously discussed in terms of modeling, simulations, parametric,and experimental studies.

Experimental studies on a combined refrigeration/power generation system activated by low-grade heat

Energy ◽  
2014 ◽  
Vol 74 ◽  
pp. 59-66 ◽  
Author(s):  
Wei Han ◽  
Qiang Chen ◽  
Liuli Sun ◽  
Sijun Ma ◽  
Ting Zhao ◽  
...  
Keyword(s):  
Power Generation ◽  
Experimental Studies ◽  
Low Grade ◽  
Generation System ◽  
Power Generation System ◽  
Low Grade Heat

Joining Techniques for Novel Metal Polymer Hybrid Heat Exchangers

2019 ◽  
Author(s):  
Gowtham Kuntumalla ◽  
Yuquan Meng ◽  
Manjunath Rajagopal ◽  
Ricardo Toro ◽  
Hanyang Zhao ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Waste Heat ◽  
Cost Effective ◽  
The United States ◽  
Thermomechanical Properties ◽  
Low Grade ◽  
Ongoing Work ◽  
Metal Metal ◽  
Low Grade Heat ◽  
Metal Polymer

Abstract In the United States, over 50% of the unrecovered energy from industrial processes is in the form of low-grade heat (< 220°C). Materials and maintenance costs of common heat exchangers are typically too high to justify their usage. Polymers, though more affordable, are usually unsuitable for HX applications due to their low thermal conductivity (∼0.2 W/mK). Here, we show that metal-polymer hybrids may be attractive from both performance and cost perspectives. The use of polymers further increases the resistance to corrosion by sulfuric and carbonic acids often present in flue gases. An ongoing work explores different configurations of layered polyimide-copper macroscale hybrids for heat exchanger applications using numerical simulations. This paper explores a manufacturing pathway for producing such layered hybrid tubes that involves directly rolling and bonding tapes made of polymer and copper foil into tubes. A critical problem in the fabrication process is the bonding of metal and polymers. We explore approaches involving adhesives (epoxy, acrylic and silicone) for metal/polymer interfaces and direct welding (ultrasonic) for metal/metal interfaces that can be integrated into the manufacturing process. We report characterizations of the thermomechanical properties of these joining processes. This work paves the way for realizing cost-effective manufacturing of heat exchangers for low grade waste heat recovery.

scholarly journals DEVELOPMENT OF HIGH EFFICIENT SHELL-AND-TUBE HEAT EXCHANGERS BASED ON PROFILED TUBES

2020 ◽  
Author(s):  
Djamalutdin Chalaev ◽  
◽  
Nina Silnyagina ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Hydraulic Resistance ◽  
Heat Exchangers ◽  
Experimental Studies ◽  
Corrugated Tube ◽  
The Heat Transfer Coefficient

The use of advanced heat transfer surfaces (corrugated tubes of various modifications) is an effective way to intensify the heat transfer and improve the hydraulic characteristics of tubular heat exchangers. The methods for evaluating the use of such surfaces as working elements in tubular heat exchangers have not been developed so far. The thermal and hydrodynamic processes occurring in the tubes with the developed surfaces were studied to evaluate the efficiency of heat exchange therein. Thin-walled corrugated flexible stainless steel tubes of various modifications were used in experimental studies. The researches were carried out on a laboratory stand, which was designed as a heat exchanger type "tube in tube" with a corrugated inner tube. The stand was equipped with sensors to measure the thermal hydraulic flow conditions. The comparative analysis of operation modes of the heat exchanger with a corrugated inner tube of various modifications and the heat exchanger with a smooth inner tube was performed according to the obtained data. Materials and methods. A convective component of the heat transfer coefficient of corrugated tube increased significantly at identical flow conditions comparing with a smooth tube. Increasing the heat transfer coefficient was in the range of 2.0 to 2.6, and increased with increasing Reynolds number. The increase in heat transfer of specified range outstripped the gain of hydraulic resistance caused by increase of the flow. Results and discussion. CFD model in the software ANSYS CFX 14.5 was adapted to estimate the effect of the tube geometry on the intensity of the heat transfer process. A two-dimensional axially symmetric computer model was used for the calculation. The model is based on Reynolds equation (Navier-Stokes equations for turbulent flow), the continuity equation and the energy equation supplemented by the conditions of uniqueness. SST-turbulence model was used for the solution of the equations. The problem was solved in the conjugate formulation, which allowed assessing the efficiency of heat exchange, depending on various parameters (coolant temperature, coolant velocity, pressure). The criteria dependences were obtained Nu = f (Re, Pr). Conclusions. The use a corrugated tube as a working element in tubular heat exchangers can improve the heat transfer coefficient of 2.0 - 2.6 times, with an increase in hydraulic resistance in the heat exchanger of 2 times (compared with the use of smooth tubes). The criteria dependences obtained on the basis of experimental studies and mathematical modeling allow developing a methodology for engineering calculations for the design of new efficient heat exchangers with corrugated tubes.

scholarly journals Features of Calculating the Characteristics of Energy Complexes Using Low-Grade Energy

2021 ◽  
Vol 18 (6) ◽  
pp. 108-117
Author(s):  
A. V. Dmitrenko ◽  
M. A. Kolosova
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Phase Transitions ◽  
Turbulent Flows ◽  
Heat Exchangers ◽  
Stochastic Theory ◽  
Fuel Oil ◽  
Low Grade ◽  
Heavy Fuel Oil ◽  
Comparison Results

The development of stationary energy seems to be an important aspect of introduction of energy-saving technologies in transportation sector. In Russia, it is conditioned by the main provisions of the Energy Strategy of the Russian Federation until 2030. In this regard, the problem of efficient use of low-grade heat based on the organic Rankine cycle (ORC) in stationary heat energy supply units in the transport industry is urgent. In particular, this task is typical for boiler houses converted from heavy fuel oil to gas fuel. In this case, the efficiency of ORC application will primarily be determined by the efficiency of the used heat exchangers (HE) with a phase transition, as a result of which, both technically and theoretically, the problem of designing and calculating the optimal characteristics of these HE will be of great interest.The article presents a theoretical and computational model of heat transfer during phase transitions in turbulent flows based on the relations obtained by the stochastic theory of hydrodynamics and heat transfer. The modelling of the effect of turbulence during the phase transition with undeveloped boiling of the bubble mode is considered. The comparison results show satisfactory conformity of the values obtained according to the formula based on stochastic equations with the values calculated according to the empirical formula for the flow in a pipe, used in the engineering method of designing heat exchangers. The results obtained open the prospect for studying the processes of heat transfer during phase transitions in turbulent flows of HE to reduce their overall and mass characteristics, as well as to increase the energy efficiency of both the devices themselves and the efficiency of the entire energy complex.

Experimental studies on combined cooling and power system driven by low-grade heat sources

Energy ◽  
2017 ◽  
Vol 128 ◽  
pp. 801-812 ◽  
Author(s):  
G. Praveen Kumar ◽  
R. Saravanan ◽  
Alberto Coronas
Keyword(s):  
Power System ◽  
Experimental Studies ◽  
Low Grade ◽  
Heat Sources ◽  
Low Grade Heat ◽  
Combined Cooling

Experimental Study on Thermophysical Properties of Nanotubes and Nanofluids

2007 ◽  
Author(s):  
Xing Zhang ◽  
Motoo Fujii
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Experimental Study ◽  
Thermophysical Properties ◽  
Experimental Studies ◽  
Spherical Nanoparticles ◽  
Hot Wire ◽  
Transient Short Hot Wire ◽  
Different Diameters ◽  
Thermal Conductivities

This paper reviews the studies of the thermophysical properties of nanotubes and nanofluids and reports the experimental studies on the thermal conductivity of individual carbon nanotubes and nanofluids containing spherical and cylindrical nanoparticles. The thermal conductivity of a single carbon nanotube has been measured by a suspended sample-attached T-type nanosensor. The size effect of the different diameters on the thermal conductivity has been observed experimentally. The effective thermal conductivity and thermal diffusivity of Au/toluene, Al2O3/water, TiO2/water, CuO/water and carbon nanofibers (CNFs)/water nanofluids have been measured by using the transient short-hot-wire technique. The measured results demonstrate that the effective thermal conductivities of CNFs/water nanofluids are much greater than those of nanofluids containing spherical nanoparticles. However, the effective thermal conductivities do not show any anomalous enhancements and can be accurately predicted by the existing formulas.

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