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Start Over Descriptor "Heat current" Language russian
2 results on '"Heat current"'

1. Peculiarities of development and extinguishing fires at the objects where liquified petroleum gas is stored

Author

Yu. Yu. Dendarenko, V. I. Dyven, Ye. O. Tyshchenko, and O. D. Blashchuk

Subjects
heat current, water spray, nozzle, liquefied petroleum gas, Forestry, SD1-669.5
Abstract

The possibility of using sprayed water jets is established, primarily radial air jets, in vertical and horizontal planes in order to reduce the temperature of the burning Liquefied Petroleum Gas, starting from the cut-off of its expiration into free space. Various technical means of supplying water in a spray and spray nozzles for their creation, which are used in solving the problem of reducing the temperature of the burning Liquefied Petroleum Gas are viewed. It has been established that the active phase of the sprayed water jet is most effective (0,5-0,75 of the lengths), which, acting under the cut of the flame is crushed to a finely dispersed phase under the influence of a high-speed gas jet. As can be seen from the above, the heating rate of the finely dispersed water phase is increased up to the gaseous state, which leads to a decrease of the temperature of the flame in its middle combustion zone. Consequently, in the flame temperature will be much lower than the temperature of the flame cone, and, as a result, close to the extinction temperature. The authors recommend the use of modern jet-forming devices to realize this goal – nozzles NRT-5, NRT-10, NRT-20, NRS, as well as hand nozzles of the kind RSK-50, RS-А, RS-B, PROTEK. In order to cool, for example, one horizontal ground steel tank on both sides, it is necessary to use at least two hydraulic guns, which will act as maneuvering. In this case, the flow of water from the hydraulic gun with a diameter of the nozzle 25 mm will be from 16 to 18 liters per second. Therefore, the task is to find, calculate and experimentally prove the efficiency of the thermal screen, which is created in the form of a moving water surface that can effectively protect a particular physical object from the thermal impact of the heat zone. In order to reduce the flow of water to cool the tanks, the authors suggest using the NRS to create radial (flat) water jets. Application of such a nozzle allows to increase the area of simultaneous cooling of the maximum surface area per unit time due to the expansion of the angle of the spray jet spark. The water consumption does not exceed 13 liters per second.

Published
2019
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2. МЕТОД ОПРЕДЕЛЕНИЯ ЛОКАЛЬНЫХ ТЕКУЩИХ КОЭФФИЦИЕНТОВ ТЕПЛООТДАЧИ В ЭЛЕМЕНТАХ СТУПЕНЕЙ МАШИН ОБЪЁМНОГО ДЕЙСТВИЯ

Subjects
Compressor, Expander, Heat exchange, Heat current, Local coefficient of heat transfer, Natural experiment, Criterial dependence, Numerical experiment, Компрессор, Детандер, Теплообмен, Тепловой поток, Локальный коэффициент теплоотдачи, Натурный эксперимент, Критериальная зависимость, Численный эксперимент
Abstract

Эффективность машин объёмного действия (компрессоров и детандеров) зависит от характера осуществляемых в них процессов и особенно процессов теплообмена газа со стенками рабочей камеры и клапанами. При создании расчётно-экспериментального метода определения локального коэффициента теплоотдачи от газа к стенке цилиндра приняты допущения о квазистационарности процессов теплообмена и одномерном направлении теплового потока. Расчётная модель процессов создана в результате сочетания аналитического подхода с обоснованным выбором обобщенной критериальной зависимости. Использование модели позволило изучить влияние конструктивных (диаметр цилиндра, ход поршня) и режимных (степень повышения давления в ступени компрессора, частота вращения вала) показателей на величину локального коэффициента теплоотдачи при изменении угла поворота вала. Для упрощения модели предложены критериальные выражения, характеризующие изменение коэффициента теплоотдачи. Сравнение полученных с использованием программы «КОМДЕТ-М» расчётных данных с экспериментами подтверждает их хорошую сходимость., The efficiency of the spatial operation machines (compressors and expanders) depends on the character of the processes that are carried out in them and especially the processes of heat exchange of gas with the walls of the working chamber and the valves. In developing an experiment-calculated method for determining the local coefficient of heat transfer from gas to the cylinder wall the assumptions about the quasi-stationary state of the heat exchange processes and an one-dimensional direction of the heat current have been made. The estimated model of the processes was developed as a result of combination of the analytical approach with the founded choice of the generalized criterial dependence. The use of the model has allowed to study the influence of the design (the cylinder diameter, a piston stroke) and the mode (the degree of pressure increase in a compressor stage, the frequency of the shaft rotation) indexes on the size of the local coefficient of heat transfer under the change of the shaft rotation angle. For the model simplification the criterial expressions that characterize the change of the heat transfer coefficient have been suggested. The comparison of calculated data obtained with the use of the program «KOMDET M» with the experimental data confirmed their close correspondence.

Published
2014

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