Special Heat Exchanger Research Articles

Experimental analysis on the prototype of decentralised air handling unit with ball-packed regenerator

Decentralised, wall mounted ventilation is one of alternative to typical – cross flow or “heat wheel” recovery air handling units (AHU) system when it is not possible to install it. It solves problems such as the need for more space, power consumption of fans, and investment costs. This experimental study aims to analyse the performance of the unique constructed decentralised air handling unit (DAHU) prototype that has a special balls-packed regenerative heat exchanger. The development of the DAHU also aimed to simplify the operation and production of the unit to make it more affordable and easier to manufacture. As the DAHU is constructed from individually sized components, the pressure losses of the diffuser, the regenerator, the screens to hold the balls, the filter and the fan were measured and the actual DAHU airflow was determined. The general operation of the DAHU was tested in a climatic chamber to determine the appropriate cycle times for this type of device, as well as the heat recovery efficiency at different outdoor air temperatures. Five different DAHU operating cycles were analysed. It was found that the duration of supply air must be longer than the duration of extract air to achieve higher efficiency. Therefore, DAHU's subsequent heat exchanger studies were performed for four airflows. The highest DAHU heat recovery efficiency was achieved (above 70%) with a supply and extract duration of 150 s. It has been found that the efficiency of this DAHU increases with decreasing outdoor air temperature because of the storage properties of the balls. The analysis showed that this type of DAHU could be suitable for use in cooler and colder climates.

Experimental and statistical determination of thermal characteristics of the special design minichannel heat exchanger

Experimental and statistical determination of thermal characteristics of the special design minichannel heat exchanger

Thermodynamic condition of cylinder diesel group for infrastructure objects under high temperatures

The article presents the results of research on the influence of ambient temperature on the thermal state of cylinder-piston groups of diesel engines, carried out by the experimental-calculation method on diesel engines 12ChN 18/20 (M787B) and 8ChN 13/14 (YAMZ-7511.10) of autonomous sources on factory test benches. In the experimental study of the effect of temperature change on the thermal state of cylinder-piston groups, the diesels were equipped with a special water-air heat exchanger for heating the air at the suction to the compressor, and the temperature of the suction air was regulated by changing the flow rate of hot water through the water-air heat exchanger. In the experimental study, along with the thermometry of parts of cylinder-piston groups, the engine operating process was indicated, the heat balance was taken, etc.; and the experimental data of other researchers were analyzed. The results of this experimental study, as well as analyzing the results of earlier work on the effect of temperature on the thermal state of cylinder-piston groups allowed to obtain empirical dependencies of local temperatures of the walls of their parts, the distinguishing feature of which is that as variables are considered their relative (dimensionless) values, which increases the degree of experimental data. The results of the performed research can be used for the calculated estimation of the temperature level in the walls of parts of cylinder-piston groups of diesel engines of a wide class of both stationary and transport diesel engines, while providing satisfactory convergence of the calculation results with the experimental data.

Компиляция данных по оптимизации работы трубчатых печей

A great number of processing hydrocarbon raw material units operated at enterprises have heat exchangers of different designs. A significant share among them comes to the special heat exchangers that use the heat of exhaust gases when burning liquid and gaseous fuels – tubular furnaces. Depending on the specifics and type of fuel used, the furnaces differ both in design and in operational parameters. At AT units, AVT units, and gasoline secondary distillation units, HFC furnaces are used to heat hydrocarbon media and are characterized by heating temperatures from 300C° to 500°C. In the units of technological processes of pyrolysis, conversion of hydrocarbon gases, etc., simultaneously with heating and/or overheating of the raw materials, furnaces are used as reactors. The effective use of such furnaces is possible only if there are used engineering methods predicting changes in the technological flow, created on the basis of reliable analytical and experimental materials. The available data is insufficient to develop measures 
 to improve the efficiency and reliability of these units. There are discussed the results of analytical studying the optimizing the operation of tubular furnaces, identified the main disadvantages during their operation, determined methods for assessing the wear of the elements of the apparatus depending on the technological modes (temperature, pressure, medium) and the material of execution in the process of technical diagnostics of equipment to ensure industrial safety. The issues of the influence of design features and of organizing the combustion process of nozzles on the quality indicators of tubular furnaces are considered. The main directions of increasing the energy efficiency of radiant and convection chambers of tubular furnaces are defined.

Evaluation of the effectiveness of air heating of the icebreaker anti-icing device at the compressor inlet

Anti-icing devices that provide increased ice penetration are widely used on modern icebreakers. The devices based on the pneumatic pressurization of the icebreaker hull with air pumped by a special compressor are most common. When operating at low temperatures, there is a danger of compressor failure due to icing of the compressor intake tract. To protect the receiving path, it is necessary to increase the temperature of the air entering the compressor to safe values. Possible heating methods are recirculation of compressed air in the compressor and its heating in a special heat exchanger. A diagram of an anti-icing system that allows you to implement both methods of air heating is presented in the paper; the principle of its operation is described. An urgent problem of selecting the most preferred method of air heating is considered in the paper. As an evaluation criterion, it is proposed to use the energy costs necessary to ensure air heating, cooling parameters of modern internal combustion engines with a high level of boost and advanced engines. To solve this problem, an algorithm that takes into account the features of the operation of the anti-icing device compressor, the requirements for the temperature of the receiving air, the properties of heat carriers is proposed. The calculation method is based on the classical equations of thermodynamics and heat transfer. The results of the calculations performed allow us to compare the energy costs for ensuring an increase in air temperature to the required values when using various methods of heat supply. The conclusions drawn on the basis of the calculations carried out allow us to conclude that the most rational way to warm up the intake air of the compressor of the anti-icing device is the joint use of recirculation and a heat exchanger. A promising direction for improving anti-icing devices is the optimization of the temperature modes of the compressor operation, rationalization of the supplied heat distribution, automation of the control for the temperature regime of the pneumatic boost.

Experimental and numerical study on a novel fanless air-to-air solar thermoelectric refrigerator equipped with boosted heat exchanger

Peltier cooling systems are generally small, portable and simple in operating principle compared to conventional vapor compression cooling systems. For these reasons, Peltier cooling systems are proposed widely to use in the field. In studies on Peltier coolers presented in the literature, equipment such as pumps and fans is used and this causes noise and vibration. In order to resolve these problems and negative effects, a cooling system was designed and manufactured using completely motionless elements. Additionally, the electricity energy need of this thermoelectric cooling chamber is fully met by solar energy. This study was investigated both experimentally and numerically by using computational fluid dynamics (CFD) methods. By designing a special heat exchanger in the produced air-to-air cooler system, it has been proven that, the Peltier system can work effectively without the need for any elements such as fans. Then the effects of the voltage values applied to the system and the number of Peltier modules have been investigated. The experiments were carried out at 4 different voltage values (1.5, 2.0, 2.5 and 3.0 V) and in 3 different Peltier numbers (1, 3 and 5) in consecutive connections. According to the obtained results, the most suitable situation for reducing the temperature of the cooling chamber were obtained as the voltage was at a maximum of 3 V and the Peltier number was maximum (5 Peltiers mode), where the internal temperature of the cooling chamber decreased to 11.28 °C. It was observed that, the coefficient of performance (COP) values decreased over time in all experiments. Considering the data taken at the beginning of the experiments, the maximum COP value was obtained as 0.04 when 1 Peltier and 1.5 V voltage were applied.

Utilizing flue gas low-grade waste heat and furnace excess heat to produce syngas and sulfuric acid recovery in coal-fired power plant

To reduce fossil resource consumption and air pollution, the effective utilization of furnace's redundant heat during peak shaving period, carbon dioxide emission reduction and flue gas waste heat recovery are three significant issues for energy saving and emission reduction of coal-fired power plants. However, these three aspects are considered separately in the past. In this study, an innovative design is proposed, in which the high and medium-grade heat during peak-off period is used for methane reforming reaction heating, while the low-grade waste heat of flue gas is used as the heat source for carbon capture process. The captured CO2 is employed as feedstock of methane dry reforming reaction to produce syngas. Meanwhile, sulfuric acid is recovered from flue gas in a special heat exchanger. Results show that this design can reduce by 445132.2 tonne of CO2 every year while the max output rate of syngas's high heating value and mass are 17,777 GJ/d and 601.7 t/d (with H2/CO = 0.618). Meanwhile, it can recover H2SO4 of 14,649 t/yr. This design not only recovers the heat energy of coal-fired power plants, but also realizes the capture and utilization of CO2, which deeply embodies the concepts of energy conservation and environmental protection.

Analysis of Efficiency of Thermopressor Application for Internal Combustion Engine

Contact cooling using thermopressor technologies is a promising direction for the development of energy-efficient technologies. This technology is based on the implementation of the thermo-gas-dynamic compression effect in special contact heat exchangers that consists of increasing the pressure while decreasing the temperature during the evaporation of a finely dispersed liquid injected into a gas flow moving at a speed close to sound. Upon application of the thermopressor for charge air cooling of the engine, the following result was obtained: an increase in the air pressure after the turbocharger by 340 to 480 kPa. The thermopressor can be used as a boost stage after the turbocharger, resulting in the reduction of a basic turbocharger compression work and the increase of engine power output accordingly. Reducing the work allows for the same air flow rate on the internal combustion engine to reduce the compressor power by 10 to 12%. This increases the temperature of the exhaust gases at the inlet of the exhaust boiler by 10 to 15 °C and boiler steam capacity, resulting in an increase in the power output of the utilization turbine generator with a corresponding reduction in the fuel consumption of the diesel generator of the ship power plant by 2 to 3%.

OBTAINING AND PROPERTIES OF NANOSCALE SOLID-STATE HEAT STORAGE WITH CARNAUBA WAX

Latent thermal energy storage using phase change materials has attracted interest in the use of solar and other types of energy due to their ability to provide high density lateral energy storage. Materials with a latent heat of storage have become attractive for their use in many branches of human activity. However, the materials use is often limited by problems of low thermal conductivity, the transition from a solid to a molten state causes difficulties in storing materials in a container, and special heat exchangers are needed to increase the energy cost. The solution to the above problems may be to create solid-state, form-stable heat storage elements. In this work, a number of shape-stable materials with a phase transition were obtained from melts by mixing halloysite nanotubes with carnauba wax in order to improve the heat accumulation characteristics. Halloysite nanotubes were mixed at elevated temperatures with carnauba melted wax and rapidly cooled to prevent the nanotubes sedimentation. As a result, a series of solid wax/nanotube samples were prepared with weight ratios of 70/30, 60/40 and 50/50. Pure wax showed a accumulation heat of the solid-to-liquid phase transition of 189.09 J/g. Carnauba wax has a latent heat greater by about 25 % compared to paraffin. Composite materials had significantly lower latent heat, respectively, 99.39 J/g for 70/30, 90.25 J/g for 60/40, and 81.26 J/g for 50/50 samples. Elemental mapping of the nanomaterial revealed a nanotubes uniform distribution in the wax. According to the data of X-ray analysis, as a result of the composite materials preparation, the components did not form new crystalline phases, but they were physical mixtures. When heated, the components did not chemically interact with each other, which is useful for the accumulation of thermal energy by materials. Analysis of the IR spectra of the samples confirmed the change in the absorption bands of functional hydroxyl groups at 3696 sm–1 (Al–O–H) and 3621 sm–1 (Si–O–H). In primary nanotubes, the intensities ratio of silanol to aluminol groups is greater than unity, while in the composite it is already less than this value. This manifestation can be explained by the fact that, during the wax melting, the interaction of wax molecules on the outer surface of the nanotubes occurs. Bibl. 16, Fig. 5.

Angle of inclination and radiation intensity variation effects on the flat plate solar collector’s performance using graphene oxide (GO)-water nanofluid

Flat Plate Solar Collector is a special heat exchanger instrument that transforms solar radiation energy into heat energy. Various attempts have been completed to improve the flat plate solar collector’s performance. One of them is by developing advanced heat transfer fluid with better thermophysical properties than base fluid. Further, the flat plate solar collector’s inclination angle and radiation intensity were investigated to identify the most optimal solar radiation angle of incidence. This study discusses the use of a 0.006% graphene oxide-water nanoparticle toward the nanofluid’s thermophysical properties, sufficient radiation intensity of flat plate solar collector performance, as well as the inclination angle of flat plate solar collector toward the collector’s performance. The used radiation intensity variations were 415 W/m2, 515 W/m2 and 615 W/m2. Meanwhile, the radiation used in this study was from a sun simulator 750 W/m2. In each radiation intensity variation, the inclination angle test of 30°, 45°, and 60° for the flat plate solar collector were carried out. This study was expected to discover the best performance of graphene oxide-water nanofluid usage, collector’s inclination angle variation, and radiation intensity variation.

Experimental investigation on the flow-induced vibration of spatial bended section of heat exchanger tubes

Flow induced vibrations in heat exchanger tubes have led to numerous accidents and economic losses in the past decades. The vibration characteristics of traditional heat tubes have been studied comprehensively through experiment, numerical simulations and theoretical analysis. Special tubes with spatial bended forms possess the great performance in nuclear engineering. The present work is motivated to understand the unclear flow-induced vibration features of these original heat exchanger tubes. An experimental system including of the tested objects are designed in water environment. The vibration responses and frequencies of spatial bended section of the heat exchanger tubes are tested and analysed. The results show that the spatial-bended tubes are safe enough to suffer the water flow within the velocity of 1m/s. The considerable vibration responses are in the bended areas with square configure, which should be specifically designed. The present work can be a guide for the special heat exchangers in nuclear engineering.

Experimental energy improvement of a special design heat exchanger-based hybrid solar collector for a photovoltaic module square surface.

Solar cells convert a part of the solar irradiance into electrical energy, and the remaining produces heat, which can be converted as a thermal energy accumulated in the module. This conversion depends on the solar cells temperature. Since conversion efficiency is very low, 5-20%, this investigation proposes an optimal combination of a photovoltaic module with a specially designed heat exchanger in order to improve the conversion energy efficiency. So, an experimental prototype of a photovoltaic thermal collector, with a special heat exchanger design for a PV module square surface is built and tested outdoor. The system is constituted of a PV module with square surface and a heat exchanger with a copper tube, in a spiral form. In order to assess the effect of the exchanger design on hybrid system performance, a comparison with a traditional photovoltaic module is done. During the experimental tests, various parameters were measured, such as solar irradiance, ambient temperature, coolant inlet/outlet temperature and surface temperature of the device. Based on the obtained results, it has been found that the use of the new PVT decreases the PV cells temperature in the order of 20°C. A consequence of that shows that the electrical power increases, by 6 W; moreover, the electrical energy efficiency goes from 7.93 to 9.65%, while the thermal energy efficiency of the PVT reaches 74.3%. The overall energy efficiency for the same system achieved was 84 %. Therefore, the energy loss is minimized, reaching 16%.

Research on the issue of using the heat of combustion products for heat supply of greenhouses

Cultivation of agricultural crops in winter season is carried out in special greenhouses. For heating greenhouses, a huge amount of heat energy is consumed. In the conditions of Turkmenistan, up to 1500 tons of standard fuel per year is consumed to heat the greenhouse with an area 1 hectare. The increase in heating costs leads to an increase in the prices of grown products. Therefore, saving fuel energy in the greenhouses is one of the most important economic factors. Possibilities of using the heat of the combustion products of steam boilers at the Mary State Electric Power Station (Turkmenistan) for heating greenhouses are discussed in the article. For this purpose, a special contact heat exchanger is installed on the line of the outgoing combustion products of steam boilers. In the experimental facilities, water is injected from top to bottom, and combustion products move in the opposite direction. In this case, the temperature of the combustion products decreases from 120-150 °C to 30-40 °C. The temperature of the cooling water of the combustion products rises from 10-20 °C to 40-45 °C. To increase the contact surface of water and gas in a contact heat exchanger, spray-type layer conductor is used. A distinctive feature of the experimental facility is the use of local materials as a spray-type layer with a conductor. For subsoil heating of greenhouses, water is supplied with the temperature of 40 °C, and for the raise of the vegetables grown in them water is supplied with the temperature of 22-25 °C. The use of the heat of combustion products to heat greenhouses is of great importance both for saving fuel and for purifying the environment from harmful emissions.

A novel design of low-grade waste heat utilization for coal-fired power plants with sulfuric acid recovery

Nowadays, serious resource shortages and environmental pollution remain puzzle for sustainable development of mankind. Energy conservation and emission reductions are inevitable historical trends, it must be reflected in idea and implemented in behaviour. Coal-fired power plants account for a great portion of energy supply, resource consumption and pollutant emissions in the same time, so it’s an essential field to implement the energy conservation and emission reduction. To recover the low-grade waste heat of flue gas, a novel design that couples organic Rankine cycle and absorption refrigeration system with sulfuric acid recovery is proposed and applied in a 1000 MW coal-fired power plant. Sulfur dioxide in the flue gas is oxidized to sulfur trioxide when flows through catalyst beds, then the sulfur trioxide is condensed to sulfuric acid in a special heat exchanger. A binary zeotropic mixture with mass ratio of 0.303:0.697 is adopted for organic Rankine cycle. After a degree-of-freedom analysis, eight independent variables are chosen as design variables to simplify the numerical model of absorption refrigeration system. Results show that the combined system can achieve a net power output of 8055 kW and a refrigeration capacity of 25493 kW. Meanwhile, a sulfuric acid production rate of 2123 kg/h can be realized ideally. This waste heat recovery system enhances the thermal efficiency of power plant case unit for 0.64% and the capital investment can be recovered within 5 years.

Device for Differentiated Cooling of Products in a Tunnel Furnace

The design of a device for supplying differentiable flows for cooling products with different enthalpy values is presented. An algorithm has been developed to control the system for extracting hot air from the cooling zone at the junction of the cooling and firing zones for feeding into the mixing chamber with atmospheric air and then to the dryer. At the same time, part of the selected hot air enters a special sectional heat exchanger, where it is converted into two cooling flows with different enthalpies of heat agents.

Device for differentiable cooling of products in a tunnel furnace

The design of a device for supplying differentiable flows cooling products with different enthalpy values has been developed. An algorithm has been developed to control the system for extracting hot air from the cooling zone at the junction of the cooling and firing zones for feeding into the mixing chamber with atmospheric air and then to the dryer. At the same time, part of the selected hot air enters a special sectional heat exchanger, where it is converted into two cooling flows with different enthalpies of heat agents. Ill. 2. Ref. 6.

Aluminum nitride as an alternative ceramic for fabrication of microchannel heat exchangers: A numerical study

Advances in micro electro mechanical systems (MEMS) necessitate utilizing efficient types of materials which are capable of dissipating high heat transfer rates. Aluminum nitride (AlN) as a member of advanced ceramics family, offers remarkable thermal conductivity which makes it suitable candidate in manufacturing of special and high-tech heat exchangers. The present work aims to investigate the application of a micro-sized heat exchanger made of AlN. According to the performed numerical simulations using Comsol Multiphysics, AlN made heat exchanger showed remarkable heat transfer enhancement of 59%, compared to the Al2O3 made one. Such a considerable improvement can be attributed to the higher thermal conductivity of AlN in comparison with Al2O3. The effectiveness of the heat exchangers were calculated for both AlN and Al2O3 made heat exchangers, and a 26% improvement was observed using aluminum nitride.

Állóhengeres kondenzátor rezgéstani vizsgálata

One of the most commonly used pressure vessels are the heat exchangers, in which the heat transfer operation takes place, the higher enthalpy medium transmits energy to the other lower enthalpy medium. These equipment are used in refrigeration systems, heat engines, metallurgy, chemical and many other industries. This study presents a theoretical and practical investigation method of the eigenfrequency of such a special heat exchanger, a vertical condensator.

Increase of heat utilization coefficient of micro-TPP fuel based on ice with air-cooling due to cogeneration

The market is widely represented by a number of micro HPP (gasoline generators) based on internal combustion engines (ICE) with air cooling. Such setups are used in everyday life, by professional builders, geologists, soldiers and rescuers in the areas of emergencies, and in the regions with lack of infrastructure. Improving the efficiency of such plants will reduce the amount of fuel supplied in the areas of their operation. This paper shows the main provisions of the research technique of the experimental cogeneration heat and power plant on the basis of an air-cooled carburetor combustion engine which is based on the mechanism of energy balances. The working capacity of the technique on various loads of the plant operation is shown. The conditions for determining the effect which consist in bringing the comparable variants to the same energy potential on the output of products are formulated. As comparison variants, it is necessary to consider electric power supply from the gas generator, and heat supply from the heat gun which, in turn, can use gas, liquid fuel or electric power as the primary energy carrier. The basic schemes of realization of cogeneration in the conditions of reduction to the same energy effect are presented. It is shown that the use of cogeneration obtained from heat of air flow cooling the cylinder head for micro HPP based on carbureted ICE with air cooling increases the coefficient of fuel heat utilization () by 1.52 times. The setup with 2.4 kW capacity for 3035 minutes can increase the temperature of the room air in the volume of 150 m3 (for example, in a staff or medical room) by  3C at  = 0.3. It is shown that cogeneration for mini-HPPs on the basis of air-cooled ICE after installation of a special heat exchanger for waste gas heat recovery allows increasing the fuel heat utilization coefficient up to  = 0.5. It is shown that a gasoline generator with cogeneration is more efficient than a gasoline generator in combination with a heat gun and due to fuel cost saving can be renewed every four years.

An analytical theory for the strength solution of tubesheets in floating-head heat exchangers with back devices

In this paper, a special floating-head heat exchanger which has back devices connected to its floating end is introduced. For the strength calculation of two tubesheets in this kind of floating-head heat exchangers, an analytical theory is proposed. Deformations and stresses at tubesheets and tubes under the shell-side pressure or tube-side pressure are evaluated. It is found that the theory is accurate in terms of stress distributions at the tubesheets through numerical verification. With some modifications, the theory can be applied to the general floating-head heat exchangers without back devices. In addition, the proposed theory can be programmed to achieve light-weight analysis of the floating tubesheet and even the heat exchanger by changing structural parameters.