Search

The paper proposes a design of a condensing heat exchanger of thermosyphon loop heat pipe for cooling of electrotechnical box. The heat pipe appears to be a very good cooling device that does not require any mechanical device in its construction. A heat pipe is a structurally simple device capable of transmitting high heat flows over relatively long distances. It may be of circular or other cross-section. If one part of the heat pipe is heated - the evaporator and the other cooled - the condenser, there is a constant evaporation and condensation of the working fluid. The section between the evaporator and the condenser where there is no phase change is called adiabatic section. The heat transfer in the heat pipe is based on the phase change principle. The design of the condensing exchanger must ensure condensation of the vapor phase and heat the environment to the surrounding environment in an ideal state only by natural convection. The article describes the design of a condensing exchanger and the impact of the amount of working fluid on performance heat pipes. [ABSTRACT FROM AUTHOR]

Liquid metal heat transfer systems are a technically attractive option to increase the efficiency of CSP plants. Sodium as heat transfer medium is promising especially due to high heat transfer rates. In this paper, basic considerations are made to match the requirements of a small-scale loop with sodium as heat transfer medium. The setup of the test facility KArlsruhe ReceIver test FAcility (KARIFA) to heat up this loop with a 20 kW IR laser is described. The loop is planned as an integrated design using an additive manufacturing process. Different technologies like selective laser melting (SLM) are established processes to realize an integrated design and to bring together components in one part. Some variations must be implemented to adapt these processes to liquid metal loops. The high heat fluxes also demand a flow simulation to ensure an efficient and safe operation. A Reynolds-averaged Navier-Stokes (RANS) steady state simulation was performed to show the surface and duct temperatures as well as dimensionless values to analyse the characteristics of the sodium flow. [ABSTRACT FROM AUTHOR]

A mathematical model of thermal process in an electrical machine was built as an example, presented as a three-layer cylinder where internal heat sources operate in one of the layers and heat is submitted to the other two by means of heat conduction. A method of solving the boundary-value problems for heat conduction equation in a complex area -- a multi-layered cylinder with internal heat sources operating in one part of the layers and external ones in another part, is proposed. A method of problem solution in conditions of uncertainty of one of the boundary condition at the layers interface with conductive heat exchange between the layers is reviewed. The principle of method lies in the averaging of temperature distributions radially in the internal layers. As a result of transformations at the layers interface a boundary condition of the impedance-type conjugation appears. The analytical and numeric-analytical solutions of simplified problems were obtained. [ABSTRACT FROM AUTHOR]

In this work, we consider the inverse source problem related with heat transfer in a inhomogeneous object when the temperatures at the surfaces are changed in time and available for measuring. This problem arises in thermal monitoring of heat treatment, in non-destructive testing for building, structure and material inspections. The mathematical model of heat transfer is represented as one-dimension heat conduction problem for a parabolic PDE with unknown time-depend source term. In this problem, the source function must be recovered from the given boundary conditions that are formed from temperature measurements. Then the thermal fields at the internal points of the object must be calculated. We reduce the original inverse problem to an integral equation describing the explicit dependence of the source function on the given boundary functions. Also we propose the computational method for determining the source function from resulting integral equation. The applicability and efficiency of method is evaluated by comparing the numerical solutions of integral equation with the test functions. The computational results illustrate the sufficient reliability of the proposed scheme. [ABSTRACT FROM AUTHOR]

The orthopedic oven is one of the tools used in the world of health. Until now, the orthopedic oven needs are still imported from other countries. The orthopedic oven is an oven that is used to heat plastic resins such as polypropylene quickly and evenly. The operation of this oven uses a large electric power and the purchase price is also relatively expensive so usually only used in large orthopedic workshops. This makes meeting the needs of the use of the orthopedic oven is limited so there needs to be an orthopedic oven design with adequate power for the home industry at a low cost. This design analysis using the calculation of heat transfer that occurs in the oven such as internal force convection, conduction, or un-steady conduction to obtain critical wall thickness values that must be used to minimize heat loss that occurs and the time needed to heat polypropylene resin. Based on the analysis of data calculations performed, obtained to reduce the heat loss that occurs need to use a gypsum board (k=0,132 W/m°C) with a thickness of 0,28 m, and the time required to heat the polypropylene to reach a temperature 185°C is 20,6 minutes. [ABSTRACT FROM AUTHOR]

The paper is concerned with the thermodynamic analysis of a multi-stream heat exchanger system for the Allam cycle and the development of a regenerator heat flow chart. The multi-stream heat exchanger thermodynamic analysis and development procedure are described in detail. The regenerator system constructed of five double-flow heat exchangers has 2.5% lower heat power than the ideal heat exchanging system. Besides, a subsequent flow interaction principle for the transfer of a maximal heat amount is proposed: it is necessary to begin with the cooling of the heating flows with minimal temperatures. [ABSTRACT FROM AUTHOR]

This contribution presents a processor farming method in connection with a multi-scale analysis. In this method, each macro-scopic integration point or each finite element is connected with a certain meso-scopic problem represented by an appropriate representative volume element (RVE). The solution of a meso-scale problem provides then effective parameters needed on the macro-scale. Such an analysis is suitable for parallel computing because the meso-scale problems can be distributed among many processors. The application of the processor farming method to a real world masonry structure is illustrated by an analysis of Charles bridge in Prague. The three-dimensional numerical model simulates the coupled heat and moisture transfer of one half of arch No. 3. and it is a part of a complex hygro-thermo-mechanical analysis which has been developed to determine the influence of climatic loading on the current state of the bridge. [ABSTRACT FROM AUTHOR]

The ITER cryogenic system will have to cope with substantial dynamic heat loads due to the magnetic field variation and the production of neutrons generated by the fusion reactions. This will induce large pressure variations in the primary cooling loop of the superconducting coils, which results in the large power variation to the helium refrigerator. The HELIOS test facility, developed at CEA-Grenoble, and initially designed to study the pulse mitigation of the JT-60SA central solenoid cooling circuit (in order to smooth the pulsed load and test components), was adapted to the ITER cooling loop requirements. This paper presents the experimental results concerning the specific ITER analysis. We reproduce experimentally the pressure variation of the Central Solenoid (CS) loop predicted by a numerical model, and observe the behaviour of the circulating pump in these conditions. The investigations of the heat load smoothing methods, using the circuit of Toroidal Field Structures, such as the pulse mitigation by temporary by-pass of the flow of the Structure cooling loop, and variation of the speed of the cold circulating pump, are also presented. [ABSTRACT FROM AUTHOR]

The superconducting magnets of the tokamak JT-60SA are cooled by means of forced flows of supercritical helium at 4.4 K and 0.5 MPa. The closed loops transfer heat from the magnets to the refrigerator through heat exchangers immersed into a saturated liquid helium bath. An experimental loop was designed to represent a 1/20 scaled down mock-up of JT-60SA central solenoid cooling circuits. This design for keeping the same transit times in the helium circuits, aims at observing the thermally induced transients in the closed loop. Indeed, heated section simulates the variable loads coming from the magnet circuits. A series of experiments was performed with pulsed loads in an isochoric configuration of the loop. The cold circulator has been characterized under pulsed operation and its performances are addressed. Mass flow regulations at the interface of the refrigerator were tested to smooth the pulsed loads with the saturated liquid bath acting as a thermal buffer. Knowledge of the pulsed loads effects on the cryogenic components is important in view of a safe operation of the cryogenic system. [ABSTRACT FROM AUTHOR]

The presented paper shows the possibility of using holographic interferometry and hot-wire anemometry in the research of heat transfer from impingement pulsatile flow. The intensity of heat transfer in the case of impingement flow is often measured with glue-on heat flux sensors, or by indirect methods such as naphthalene sublimation. All these methods have a response time too long for measuring instant values of the heat transfer coefficient on a surface cooled/heated by impingement pulsatile flow. This shortcoming should be overcome by using CTA glue-on probes or, preferably, by using optical methods such as holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain the parameters sufficient for the studied case. This setup is not light efficient like the Mach-Zehnder type but has double sensitivity. The results from the holographic interferometry experiments will be compared with the temperature field achieved by methods of hot-wire anemometry. [ABSTRACT FROM AUTHOR]

In this paper a new method for the computational analysis of the dynamic behavior of bodies involved in calorific transfer processes is presented. This technique facilitates the thermal studies carried out in the engineering and science fields. The solution presented is based on Laplace direct transform application in order to solve the differential equations that characterizes one-way heat conduction. In this way, fast and precise results of the dynamic process are obtained, without the need of applying finite differences methods which result in high computational loads. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) process composes a complex system, where chemical reaction and heat and mass transfer interact with each other. And these macro-scale phenomena are deeply related to micro-scale mechanics. Hence multi-scale analysis is required to understand these complicated phenomena and to develop full-scale simulator of the CVD reactor. In this paper, we present the macro-scale simulation by the DSMC method. In those reactors, sometime the important species such as the reactive intermediates have extremely low density ratio. This causes the large statistical fluctuation in the DSMC method, where the number of particles and the calculation time are limited. We propose a new numerical method for this kind of problem and the whole process of silicon CVD is simulated by the new method. We simulate the following CVD process: the gas mixture of silane and hydrogen forms a free expansion jet through a nozzle orifice at the top of the reactor and interact with the heated substrate that is set vertical to flow, where silane decomposes into silylene and silane and silylene deposit onto the surface. It is confirmed that the new method is very effective and make it possible to analyze the CVD process more precisely. [ABSTRACT FROM AUTHOR]