Heat balance of the military vehicle

In modern combat vehicles there are very often used observation devices with the capability of operating in the infrared. They allow detecting heat emission. It is very important to reduce such situation on the battlefield; therefore generated heat masking or reducing systems are used. The article presents the heat balance of the military vehicle, impact of heat amount on detectability and solutions reducing or changing the thermal image which impedes recognition.

A Model of Optimization and Control the Thermite Kit for Aluminothermic Welding

Thermite welding (TW) is now widely used all over the world to weld, maintenance and modernization railway and tram rails [1]. The main materials from the thermite composition (TC), results from manufacturing scraps, which can be retrieved all over the country. Exothermic welding (EW) which is based on the exothermal reaction between iron oxides (FeO, Fe2O3 and Fe3O4) and aluminium powder, takes place at temperatures up to 3500 °C and during casting rail ends are melted in order to be welded.In was studied the thermal effects of the aluminothermic reduction reactions of the iron oxides, which were dosed in different percentages. The aluminothermic reaction efficiency is given by strictness in the ratio of the TC selection and mainly in the iron oxides types. Their correct dosage makes possible the control the exothermic reaction (ER) effect. Also it is revealed the effect of particle size from thermite powder (TP) on the thermite dynamics reactions. Is also presented a model of optimization and control the thermite kits (TK) for aluminothermic welding (AW). Finally, the TK composition can be calculated from "QUARK1" Diagram, as function of the heat amount necessary for the welding.

Research on Physical and Hydration Heat Characteristics of the Multi-Component Cementitious Materials

In order to get the various strength grade of the cement and know the characterics of the hydration heat of multi-component cementitious binders, in this paper, we get the component-cement with low content clinker and high content admixture. The cement properties, the hydration heat properties and the self-construction properties of composite cementitious binders with different rations of the mixture are tested.The results showed that the 56th compressive strength can get 58.4Mpa which is 4.4MPa higher than the traditional cement.The hydration heat of cement with high dosage admixture has a greatly reduction. The heat amount and the hydration release speed are both lower than the tradtional . The value of self-constriction is obviously decreased.

Cooling Thin Parts of Pressure Casting Moulds by Means of Liquid CO2

To ensure optimal temperature conditions during casting cycle the pressure casting moulds are equipped with cooling systems. These days the cooling systems used in the most of Czech foundry plants enable pre-heating of pressure casting moulds to the working temperature before start-up of production and during casting operation to keep optimal temperature balance among the casting and the mould. Pressure casting mould temperature balance is provided by system of mutually connected channels which are mostly parallel with parting line and inside those the heat transfer medium flows. However such a system allows removal only limited heat amount from the most overheated places of the casting mould and does not allow heat removal from cores of small diameters. This inhomogeneous heat removal causes porosity of the casting in certain areas and also lifetime of the pressure casting mould is dramatically reduced. Cooling by means of liquid CO2 was developed as one of the new cooling possibilities for such places in the pressure casting mould where the heat is concentrated and for standard cooling systems it is too complicated to fully control the heat processes there. The paper deals with the behaviour monitoring of the new cooling system utilizing the potential of liquid CO2. This system was applied into pressure casting mould core and its final impact on the casting quality in the close surrounding was observed.

Some characteristics of the resultant air flow from motions induced by ventilation and heat source in a two-dimensional enclosure

Ventilated air flow in an enclosure is often unsteady (turbulent) at even very low Reynolds number (Re). Meantime natural convection in a box is stationary motion at large enough Rayleigh number (Ra). This paper deals with the interaction between two those flows in a two-dimensional room. The room has one inlet and one or two outlets. A heat source locates on the floor. The numerical simulation of the interaction is carried out at some values of Re and Ra for two cases of the inlet and outlet configuration. Some interesting characteristics of the resultant flow are discovered. The heat amount released by the source and removed from the room by different types of this flow is also provided.

Experimental Investigations on the Relation of the Lubricant’s Flash Point and Quality of the Piston Made from Aluminium Alloy for its Application in Internal Combustion Engines

In the current paper there was made an attempt to develop an experimental method of physical (lubricant’s flash point Tfp) and subjective (forgings’ quality) parameters coupling for hot isothermal-like forging operation. The quality forgings could be manufactured both by high and low lubricant’s flash point. The increase of Tfp value in exothermal reaction follows to the increase of the released heat amount by the lubricant, because it needs more initial activation energy transmitted from the external source to initialize transformation of the material from one aggregate state into another (from liquid or solid into gaseous or sol-like). This can prevent the temperature decrease on the punch due to strong convective heat transfer with the environment through the building of the isolation temperature shield on the punch contact surface at the beginning of the punch stroke. On the other hand it can cause the defect building on the forgings like penetrations, which could not be eliminated during cleaning operation before mechanical treatment due to chemical interactions of the dissolved active agents, or unfilled sections.

Study on Criteria of Flushing Phenomena in Boiling Transition by Microwave Heating

In the Microwave Heating de-nitration (MH) method developed in Japan, a mixed solution of uranyl nitrate and plutonium nitrate (Pu/U mixed nitrate solution) recovered from the spent fuel in the reprocessing plant is converted directly to mixed oxide (MH-MOX) powder. This MH-MOX powder is utilized to fabricate MOX fuel with UO2 powder for FBR. The MH method is accompanied with transient boiling phenomena such as overflow and flushing. Toward high-speed and high-capacity conversion by MH-method in the future, it is required to avoid overflow and flushing and to understand optimal conditions for vessel shape design and microwave output operation. The objective of this paper is to elucidate occurrence criteria of flushing phenomena. At the first step for this objective, basic knowledge of transient boiling phenomena by the MH-method has been mainly acquired with using distilled water. From the results, it is observed that generation of singular bubble triggers flushing and distilled water just before flushing is superheated more than 10 °C in conditions that flushing is confirmed. Also, the water temperature reaches its peak, and it is almost unchanged in conditions that flushing is not confirmed. In no flushing conditions, it is found that the evaporation starts from the point where the water temperature reaches its peak, and water level is decreased gradually. Thus, the difference of thermal characteristics greatly affects whether flushing occurs. The second step, by focusing on the process before flushing occurs, we investigate flow structure, and heat amount through the temperature distribution inside the jelly just after microwave heating. Potassium chloride (KCl) aqueous solution and water are used. KCl solution is electrolyte solution same as reprocessing solution. From the results, upward flow is observed near the center of the solution in the case of the water just after microwave heating. On the other hand, downward flow is observed in the case of KCl solution. As a result of temperature distribution, the water is heated its near center, and KCl solution is heated the around. Thus, it is considered that heat amount of microwave varies depending on solution characteristics, and the difference greatly affects the flow structure. The heat amount and flow structure are critical factors that can determine transient boiling phenomena. We need to investigate transient boiling phenomena of KCl solution in the future.

The Study on Heating Running Schemes of Solar Energy Combined with Municipal Heating

The research, based on combination system of solar energy and municipal heating network, studied the running scheme of combination system of solar energy and municipal heating network through ways of experiments and theoretical calculation of the mathematical model. Firstly, the research established mathematical model of heat equilibrium of the combination system of solar energy and municipal heating network; secondly, keeping the indoor heat load steady, compared the dynamic heat load provided by solar collector with that needed by heated room at the same time,determined time spans of the network stopping service and the heat load added by the network within 24 h. In the research we took a heating period in a typical room in Shenyang for example, under the conditions of low temperature floor radiant with heating index standard of 50W/ m2 and 50°C of the average supplied water temperature, 40 °C of the return water temperature, calculated and verified the established mathematical model. The results include: when the heat load provided by solar collector is greater or less than the heat needed by the room, how many heat amount should be supplied by the running network and the amount of water flow within the network pipes correspondingly, and how long the network runs or stops. The final conclusions include: whether the running scheme of the combination system can save energy? the conditions of energy saving in running a combination system, and whether the system can bring environmental benefits.

Numerical Investigation of Thermal Characteristics in a Solar Chimney Project

In order to create interior multiclimate zones suitable for plant cultivation in a solar chimney project proposed for the World Horticultural Exposition 2016 in China, the numerical investigation is performed to a solar chimney with 2 km radius and 1 km height. The simulation methodology is validated by experimental data. The impacts of inlet height and radius to interior thermal characteristics are evaluated. It is found that the temperature field is much similar when the inlet height decreases from 3.8 m to 0.5 m. With further decrease of the inlet height to 0.2 m, its impact to temperature field is significant. The temperature field is similar though the radius of solar chimney decreases from 2.0 km to 1.725 km. Further decrease to 1.13 km results in much lower temperature field as less radiate heat is obtained. The procedure of soil surface temperature calculation is also proposed to obtain the supplementary heat amount maintaining the required temperature for plant cultivation.