DETERMINATION OF THE AVERAGE WALL TEMPERATURE OF THE PLATE IN A RECUPERATIVE HEAT EXCHANGER WITH A CORRUGATED MESH INSERT

This article discusses the issue of determining the value the average wall temperature of the plate of a recuperative heat exchanger type “air-to-air” with a corrugated mesh insert based on the results processing the data of a physical experiment to determine the thermohydraulic characteristics such heat exchange surfaces. It has been established that the temperature fi eld of heat exchange surfaces of this type is nonuniform, depends on the conditions of heat exchange and hydraulic regimes of air fl ow. Therefore, the adoption of the arithmetic means value of the measured surface temperatures as the calculated average temperature of the heat exchanger wall entails signifi cant errors in the subsequent processing of experimental data and fi nal the values of the heat transfer coeffi cients, the values the Nusselt criterion and the criterion equations of heat transfer. It is proposed to determine the average value the wall temperature of the heat exchanger based on the results of measurements the wall’s temperatures, the estimate of the coordinates the center of distribution the results of measurements the wall temperatures, the equations of heat balance and heat transfer.

Heating Performance and Ammonia Removal of a Single-Stage Bioscrubber Pilot Plant with Integrated Heat Exchanger under Field Conditions

In this study, biological exhaust air treatment was combined with a recuperative heat exchanger in one process stage. The aim of this plant development and testing is not only to reduce ammonia from the exhaust air of pig houses but also to recover thermal energy at the same time. This is intended to offset the high operating costs of exhaust air treatment with savings of heating costs in cold seasons and to use the plant more efficiently. This system was tested for the first time under practical conditions in a pig fattening house in southern Germany. Three different assembly situations of the heat exchanger were examined for 13 days each and then compared with each other. The heating performance of the plant is primarily dependent on the outside air temperature and secondarily on the scrubbing water temperature. Depending on the assembly situation of the heat exchanger, an average heating performance of between 6.0 and 10.0 kW was observed; the amount of recovered thermal energy was between 1860 and 3132 kWh. The coefficient of performance (COP) ranked between 7.1 and 11.5. Furthermore, ammonia removal up to 64% was demonstrated. A long-term investigation of the system under practical conditions is recommended to validate the data collected in this study.

Countercurrent Index Determination for the Recuperative Heat Exchangers

The recuperative heat exchangers are an important part of the industrial plants. There are a number of such heat exchangers that differ in the arrangement of the streams. The knowledge of the flow arrangement of the streams is very important from a point of view of the heat exchangers calculations. There are various calculation methods, but only one takes into account the flow arrangement of the streams directly. The quantity that takes this into account is called the countercurrent index. The article deals with the determination of this quantity for a given recuperative heat exchanger.

Heating performance of a laboratory pilot-plant combining heat exchanger and air scrubber for animal houses

Exhaust air treatment systems (EATS) are used in animal husbandry to reduce emissions. However, EATS are associated with high acquisition and operating costs. Therefore, a plant technology is being developed that integrates a recuperative heat exchanger into a biological air scrubber. The overall aim is to reduce total costs of livestock buildings with EATS by saving heating costs and to improve animal environment. In this study, a special pilot-plant on a small-scale, using clean exhaust air, was constructed to evaluate the heating performance on laboratory scale. Three assembly situations of the heat exchanger into trickle-bed reactor were part of a trial with two different defined air flow rates. In all three assembly situations, preheating of cold outside air was observed. The heating performance of the assembly situation with the sprayed heat exchanger arranged below showed an average of 4.4 kW at 1800 m3 h−1 (outside air temperature range 0.0–7.9 °C). This is up to 18% higher than the other two experimental setups. The heating performance of the pilot-plant is particularly influenced by the outside air temperature. Further research on the pilot-plant is required to test the system under field conditions.

VERSION OF A MATHEMATICAL MODEL OF PURGE VENTILATION SYSTEM WITH A COMPLEX RECUPERATIVE HEAT EXCHANGER

The aim of the study is to develop a design of an air-heating recuperator for a purge ventilation system of a building inbuilt for the purpose of utilizing lower-grade heat from ventilation gases and emissions with the associated production of thermoelectricity. An experimental design of an air-heating recuperator as part of an experimental purge unit has been developed. It includes a thermoelectric source of electromotive difference, which operates as a result of the associated conversion of heat into electricity, which allows utilizing lower-potential heat of ventilation releases from 40 ° C to 60 ° C.

Heat recovery by means of a ventilation unit

Energy consumption all over the world is constantly growing. To save energy, new technologies are being developed for the efficient use of energy resources. The goal of all new developments is to use less energy to provide the same level of energy supply for technological processes or buildings. The problem of energy saving is relevant for the ventilation system. Together with the removed air, a large amount of heat is lost, which is not advisable. In order to avoid these losses, heat recuperators began to be used, heating the cold supply air due to the warm air removed from the room. This development belongs to the field of energy saving. The goal is to increase efficiency by reheating the air after the heater with the help of a recuperator for a given temperature difference in the supply air before and after the recuperative heat exchanger. The development is a design of a ventilation unit with air removal and supply air ducts, combined into one housing with a separate, according to the “screw” principle, heat transfer wall, for use in the ventilation system in order to ensure an optimal microclimate in the room. Thus, as a result of using the presented device, the efficiency of the room ventilation unit is increased by reducing the energy consumption for heating the supply air with a heater.