THERMOPHYSICAL ANALYSIS OF THE PARAMETERS OF A BIOMASS FUELED MICRO–CHP UNIT WITH A STIRLING ENGINE

A typical scheme of a biomass fueled micro-CHP unit with a Stirling engine, including a combustion chamber, a Stirling Engine, a recuperator and water heater, is considered. A brief overview of the main biomass combustion methods used in this installation is made. Thermophysical analysis was carried out on the basis of solving a system of equations: the reaction equation for wood biomass combustion, the equations of both the general heat balance and the heat balance of parts of CHP unit, as well as the equation of energy conservation at flows mixing in the combustion chamber, taken into account the heat input and losses. The relationship for calculating the theoretical temperature in the combustion chamber and heat flux in the recuperatoris obtained. The last equation is obtained in dimensionless form. The theoretical temperature in the combustion chamber and the heat flux in the recuperator have been calculated, the influence of the main factors has been analyzed - the efficiency of heat exchange in the recuperator, the share of the total air flow passing through the recuperator, the excess air ratio, dimensionless heat losses and heat flux on the hot heat exchanger of the Stirling engine. It is shown that the temperature in the combustion chamber decreases with a decrease in the efficiency of the recuperator and with an increase in the excess air ratio. A significant influence of heat losses in the combustion chamber on the heat flux in therecuperatorwas found. Under certain conditions (high heat losses and high heat exchange on the hot heat exchanger of the Stirling engine), the recuperator is not neededatall. It is also shown that the share of the total air flow passing through the recuperator has a significant effect on the heat flux in the recuperator. Thus, when the air flow passing through the recuperator is reduced by 2 times, the heat flow is reduced by 5 times. Therefore, it is necessary to minimize the air flow bypassing the recuperator. As a result of thermophysical analysis, the optimal value of the excess air ratio was obtained, which is 1.7 ... 1.8.

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Experimental setup for studying two-phase flows in micro-and minichannels at ultra-high heat fluxes: methodology and first experimental results

Journal of Physics Conference Series ◽

10.1088/1742-6596/2119/1/012133 ◽

2021 ◽

Vol 2119 (1) ◽

pp. 012133

Author(s):

D V Zaitsev ◽

V V Belosludtsev

Keyword(s):

Heat Flux ◽

Test Section ◽

Flow Boiling ◽

High Heat ◽

Heat Losses ◽

Heat Fluxes ◽

Two Phase ◽

Experiment Versus ◽

Fast Development ◽

Phase Change Phenomena

Abstract The study of phase-change phenomena under high and ultra-high heat fluxes is urgent because of fast development of electronics and microelectronics. We have developed a test section with power of 3.5 kW with a heater of 1x1 cm2 and adjustable geometry of the channel for achieving ultra-high heat fluxes in flow boiling and shear-driven liquid film experiments. The methodology of calculating heat losses in the test section is proposed and verified by flow boiling experiment versus another well studied test section. Observed trend of decrease of relative heat losses with increase in the heat flux makes it possible to assume that the heat flux as high as 2.5 kW/cm2 can be reached by this test section.

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Two-Dimensional Model of the Air Flow and Temperature Distribution in a Cavity-Type Heat Receiver of a Solar Stirling Engine

Journal of Solar Energy Engineering ◽

10.1115/1.2888169 ◽

1999 ◽

Vol 121 (4) ◽

pp. 210-216 ◽

Cited By ~ 5

Author(s):

Kh. Kh. Makhkamov ◽

D. B. Ingham

Keyword(s):

Free Convection ◽

Air Flow ◽

Heat Losses ◽

Stirling Engine ◽

Numerical Results ◽

Physical Models ◽

Heat Receiver ◽

Working Cycle ◽

Side Walls ◽

Engine Power

A theoretical study on the air flow and temperature in the heat receiver, affected by free convection, of a Stirling Engine for a Dish/Stirling Engine Power System is presented. The standard k-ε turbulence model for the fluid flow has been used and the boundary conditions employed were obtained using a second level mathematical model of the Stirling Engine working cycle. Physical models for the distribution of the solar insolation from the Concentrator on the bottom and side walls of the cavity-type heat receiver have been taken into account. The numerical results show that most of the heat losses in the receiver are due to re-radiation from the cavity and conduction through the walls of the cavity. It is in the region of the boundary of the input window of the heat receiver where there is a sensible reduction in the temperature in the shell of the heat exchangers and this is due to the free convection of the air. Further, the numerical results show that convective heat losses increase with decreasing tilt angle.

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Numerical Study of Interaction Between Natural Convection Flow and Horizontal Wind

Volume 2: Fora, Parts A and B ◽

10.1115/fedsm2007-37212 ◽

2007 ◽

Cited By ~ 1

Author(s):

S. Sakai ◽

Y. Watanabe

Keyword(s):

Heat Flux ◽

Natural Convection ◽

Large Scale ◽

Numerical Study ◽

Air Flow ◽

Three Dimensional ◽

High Heat ◽

Horizontal Wind ◽

Convection Flow ◽

And Behavior

When a large-scale fire, such as a town area fire by an earthquake disaster and forest fire, happens, there can be a fire whirlwind, which is a strong flow including strong flame and sparks. It is sometimes called a firestorm. Fire whirlwind is exposed to high heat, and possesses high heat itself. Therefore, the fire whirlwind is very dangerous. The whirlwind moves and promotes spread of a fire and may enlarge the damage rapidly. Various studies are performed about fire whirlwind, but the property and outbreak mechanism of the whirlwind are not elucidated enough till now. Therefore, in this study, we pay our attention to the flow that is a basic phenomenon of fire whirlwind, and examine the influence that a natural convection gives to outbreak and behavior of fire whirlwind by numerical computation. The numerical analysis performed three-dimensional calculation with analysis software FLUENT6.1. Firstly, a model of the fire domain is constructed. The model is referred from an example of large-scale fire at the Great Kanto Earthquake (1923 in Japan), and natural convection is observed for different heat flux. Then, it is analyzed in a similar model whether a whirlwind occurs or not, after natural convection is fully-developed with changing velocity of the air flow from the side. Furthermore, it is analyzed in a model in which a fire occurs at random whether a whirlwind occurs or not after natural convection is fully-developed with changing velocity of the air flow from the side. As a result of analysis, a whirlwind occurs. The whirlwind sometimes moves and extinct. Then, the influence that a natural convection gives outbreak of the whirlwind is evaluated with changing heat flux and velocity of wind.

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Study of hot tungsten emissive plate in high heat flux plasma on NAGDIS-I

Journal of Nuclear Materials ◽

10.1016/s0022-3115(96)00707-6 ◽

1997 ◽

Vol 241-243 (1) ◽

pp. 1243-1247 ◽

Cited By ~ 5

Author(s):

M Ye

Keyword(s):

Heat Flux ◽

High Heat ◽

High Heat Flux

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Effect of Chemical Hythane Composition on Pressure in Combustion Chamber of Engine

Alternative Energy and Ecology (ISJAEE) ◽

10.15518/isjaee.2019.10-12.036-042 ◽

2019 ◽

pp. 36-42

Author(s):

A. P. Shaikin ◽

I. R. Galiev

Keyword(s):

Natural Gas ◽

Combustion Chamber ◽

Power Plants ◽

Engine Speed ◽

Combustion Engine ◽

Fuel Mixture ◽

Maximum Pressure ◽

Chamber Volume ◽

Excess Air ◽

Scientific Papers

The article analyzes the influence of chemical composition of hythane (a mixture of natural gas with hydrogen) on pressure in an engine combustion chamber. A review of the literature has showed the relevance of using hythane in transport energy industry, and also revealed a number of scientific papers devoted to studying the effect of hythane on environmental and traction-dynamic characteristics of the engine. We have studied a single-cylinder spark-ignited internal combustion engine. In the experiments, the varying factors are: engine speed (600 and 900 min-1), excess air ratio and hydrogen concentration in natural gas which are 29, 47 and 58% (volume).The article shows that at idling engine speed maximum pressure in combustion chamber depends on excess air ratio and proportion hydrogen in the air-fuel mixture – the poorer air-fuel mixture and greater addition of hydrogen is, the more intense pressure increases. The positive effect of hydrogen on pressure is explained by the fact that addition of hydrogen contributes to increase in heat of combustion fuel and rate propagation of the flame. As a result, during combustion, more heat is released, and the fuel itself burns in a smaller volume. Thus, the addition of hydrogen can ensure stable combustion of a lean air-fuel mixture without loss of engine power. Moreover, the article shows that, despite the change in engine speed, addition of hydrogen, excess air ratio, type of fuel (natural gas and gasoline), there is a power-law dependence of the maximum pressure in engine cylinder on combustion chamber volume. Processing and analysis of the results of the foreign and domestic researchers have showed that patterns we discovered are applicable to engines of different designs, operating at different speeds and using different hydrocarbon fuels. The results research presented allow us to reduce the time and material costs when creating new power plants using hythane and meeting modern requirements for power, economy and toxicity.

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