Mathematical Model of a Sun-Tracked Parabolic Trough Collector and Its Verification

The paper presents a one-dimensional distributed parameter model for simulating the transient-state operation of a parabolic trough collector (PTC). The analyzed solar collector has a module design and is equipped with a two-axis sun-tracking system to increase the solar energy yield. The single module is composed of an evacuated tube and a set of parabolic mirrors acting as reflectors. In each of the collector tubes, two aluminum U-tubes are installed, enabling heat intake by the solar fluid. The collector is intended for household applications, as well as other medium thermal energy demand uses. During the numerical model development, appropriate energy balance differential equations are formulated for the collector individual components. The equations are solved using different schemes. As a result, a time- and space-dependent temperature series for each of the collector components and the working fluid are obtained. To select an appropriate time and spatial steps for the developed model and to verify the reliability of the results received, the collector model is also implemented in ANSYS Fluent. The results of the one-dimensional model calculations and comparisons carried out in ANSYS demonstrate considerable agreement. In particular, the values of the fluid temperature at the collector outlet, calculated using the model developed, show high consistency with the ANSYS Fluent results. Furthermore, a preliminary experimental verification of the proposed model is carried out on a test stand currently under construction. The computed and measured temperature course of the fluid at the collector outlet is compared. In this case, the results are also satisfactory.

Adsorption of naphthalene onto loess soil of Northwestern China

The naphthalene adsorption onto loess soil was studied by batch experiments, including isotherm, impact factors, and kinetics. The results indicated that (1) adsorption equilibrium conformed best to the Freundlich isotherm. (2) Loess had the best adsorption capacity for naphthalene at pH 5. (3) The ionic strength had little effect on the adsorption equilibrium in the range adopted in the experiments. (4) In the temperature range from 10°C to 30°C, the equilibrium adsorption amount had a positive correlation with the temperature. (5) The adsorption process of naphthalene to loess conformed best to third-order kinetics, and the analysis of the correlation between adsorption rate constants and temperatures indicated that naphthalene adsorption to loess was an easy, heat intake process.

The Case of the Missing Lunar Heat Flow Data Is Finally Solved

Decades-old data analyzed for the first time suggest that astronauts’ disturbance of the Moon surface increased solar heat intake, warming the ground below.

Autonomous Power Station Based on Rotary-Vane Engine with an External Supply of Heat

Rotary-vane engine (RVE) with an external supply of heat is an aggregate consisting of two modules with a common output shaft, the heating device (heater) of working medium and the cooling device (cooler) of working medium, which connected with inlet and outlet ports of modules by system of pipeworks. Each module has two rotors with two vanes on each. Between the corresponding plane surfaces of the four vanes four working volumes are formed wherein thermodynamic cycle steps: ingress, compressing, heat intake, expansion stroke, discharge, outward heat transmission are going simultaneously. The angular displacement of modules relative to one another occurs pumping the working medium through the heater and cooler, which allows the conversion of thermal energy into mechanical work. Design features of the RVE with an external supply of heat allows create a closed gas-vapor cycle. The main specified advantages of the RVE with an external supply of heat are: fewer noxious emissions, multifuel capability, high motor potential (service life). Different problems of creation external combustion engines such as structural complexity of construction units, absence of adequate mathematical model of designed RVE with an external supply of heat are also pointed. The construction of the RVE with an external supply of heat developed in Pskov Polytechnic Institute (now the Pskov State University), the operation concept of the engine, the physical processes in the chamber modules RVE with an external supply of heat during each step and the mathematical model describing the physical processes proceeding in chamber RVE with an external supply of heat modules are considered.

The Analysis of the Heat Transfer into Reactor Walls in the Thermal System and the Verification

The article presents the analysis of thermal flows into reactor walls within the semi-operational pyrolytic system. There were hydrodynamic and thermodynamic similarity theories and heat transfer by radiation laws used for the solution of this issue. The entry data for the heat transfer analysis were gained by conducted experiments. The correctness of the resulting values has been verified by measurements. The required reactor parameters, for the required heat intake, have been derived from the analytical results at the end of this article.