Study of Heat Transfer Rate in Electric Evaporators of Liquefied Petroleum Gas Using Electrothermal Modeling

In modern domestic and foreign experience of gas power supply to houses and industrial facilities located remotely from the main power station, decentralized gas power supply systems fed with propane-butane mixtures of liquefied petroleum gases from tanks are increasingly used. When using liquefied petroleum gases as the main energy carrier in gas tank systems, they are evaporated artificially in evaporators with an intermediate solid-state or liquid heat transfer agent, under conditions of its natural convection. The main operational characteristic of industrial tube evaporators of propane-butane mixtures of liquefied petroleum gases used for gas power supply from tank installations of housing and communal, industrial and industrial facilities that are remote from the main power supply stations is evaporation capacity. The evaporation capacity of industrial tube evaporators of propane-butane mixtures with a solid-state intermediate heat transfer medium is determined by the heat input from the tubular electric heaters through the aluminum casting layer. Therefore, the study of heat transfer in the solid–state intermediate heat transfer medium-evaporation coil system is the most important prerequisite for the effective operation of industrial tube evaporators of propane-butane mixtures and requires detailed research. To solve the problem of determining the heat transfer resistance between the layers of aluminum casting in contact with the surface of the tubular electric heaters group and the outer evaporation coil surface studies were performed on an electrical model. The average value of the total error of the results of experimental studies on electrothermal modeling is 3.7 %, with a confidence probability of 95 %. Recommendations are given for reducing the thickness of the layers in clear from the lower coil of the evaporative tube coil to the lower generatrix of the solid-state aluminum mass and the upper coil of the evaporative tube coil to the upper generatrix of the solid-state aluminum mass.

Effect of Carburizing on Microstructure and Weldability of 35Cr-45Ni-Nb Alloys in the Ethylene Heating Furnace

This paper presents the effect of carburizing phenomena on the microstructure and weldability of tube coils in the ethylene heating furnace. A tube coil material was used the Ni-base alloy grade 35Cr-45Ni-Nb. The specimens obtained from three different height levels of carburized tube were tested. The results from the SEM-EDS and microstructure analyses show that the carbon was concentrated in carburized tube and deposited in the solid solution and chromium carbide compound. The prediction of new weldability in the carburized tube with Nieq/Creq ratio can be used for welding repair in petrochemical industry.

Experimental and Simulation Study on the Effects of Twisted Coil Plates on the Performance of Fire Tube Boiler

Influences of twisted coil plate insert on the performance of fire tube boiler using were experimentally investigated. In this study, the twisted coil plate was placed inside the tube to illustrate boiler performance. The performances of boiler were studied in terms of operating time taken, exhaust flue gas temperature, steam temperature and boiler efficiency. The boiler was operated with 50%, 100% and without tube coil plate inserts at low and high fire burner setting. Based on the results obtained, effect of twisted plate insert and without insert were observed. There is an enhancement in boiler performance in terms of boiler efficiency. The ANSYS Fluent simulation showed the effect of width ratio and twist ratio. Therefore, the experimental results indicate that using twisted coil plate in the boiler is one of the best ways to improve boiler performance.

Comparing Saddle, Slotted-tube and Parallel-plate Coils for Magnetic Resonance Imaging

The paper is concerned with a comparison of the properties of RF coils of three configurations for MRI measurements on small animals. In comparison with the classical saddle coil the proposed modification of slotted-tube coil exhibits identical homogeneity of B1 field in a larger space. The parallel-plate coil has a satisfactory homogeneity of B1 field over the whole internal space. The signal-to-noise ratio measured for all three coils is roughly the same and is given by the magnitude of RF pre-amplifier noise. As the slotted-tube and parallel-plate coils have a lower inductance compared with the saddle coil, they can be tuned to resonance on the 200 MHz frequency even at larger dimensions. The results show that the parallel-plate coil has very good properties for the measurement of small animals.

Levenberg-Marquardt application to two-phase nonlinear parameter estimation for finned-tube coil evaporators

A procedure for calculation of refrigerant mass flow rate is implemented in the distributed numerical model to simulate the flow in finned-tube coil dry-expansion evaporators, usually found in refrigeration and air-conditioning systems. Two-phase refrigerant flow inside the tubes is assumed to be one-dimensional, unsteady, and homogeneous. In the model the effects of refrigerant pressure drop and the moisture condensation from the air flowing over the external surface of the tubes are considered. The results obtained are the distributions of refrigerant velocity, temperature and void fraction, tube-wall temperature, air temperature, and absolute humidity. The finite volume method is used to discretize the governing equations. Additionally, given the operation conditions and the geometric parameters, the model allows the calculation of the refrigerant mass flow rate. The value of mass flow rate is computed using the process of parameter estimation with the minimization method of Levenberg-Marquardt minimization. In order to validate the developed model, the obtained results using HFC-134a as a refrigerant are compared with available data from the literature.