Heat Wheel Research Articles

Investigation of the energetic and exergetic performance of hybrid rotary desiccant-vapor compression cooling systems using different refrigerants

In this study, a desiccant-based hybrid cooling system supported by a vapor compression system and a heat recovery unit (rotary heat wheel) was analyzed from energetic and exergetic perspectives during the daily working hours of an office building in Istanbul to meet the desired comfort conditions. We focus on the impact of different refrigerants; namely R32, R1234yf, R290, R134a, R600a, R245fa, and R717, on hybrid rotary desiccant-vapor compression systems. While the highest electricity consumption was obtained in the system using R1234yf, the lowest electricity consumption was achieved with R717. However, with the effectiveness of the desiccant wheel, the best results were obtained for R1234yf with those pertinent to R717 at the other extreme. Considering the total electricity consumption of the system, the highest energetic and exergetic performance parameters were achieved with the use of R717 as the refrigerant. Compared to R1234yf, the daily average energetic performance parameters obtained with R717 increased by 22.3 % for COPr, 21.8 % for COPel, and 4.7 % for COPth. Similarly, compared to R1234yf, the daily average exergetic performance parameters in R717 presented increases of 13.6 % for COPx,el, 7.5 % for COPx,th, and 8.1 % for ηx.

Оценка влияния различных газов на давление в шинах при выделении тепла

Transportation of minerals during open-pit mining works is mainly provided by heavy vehicles. One of the most dangerous accidents during the operation of vehicles in open-pit mines is the destruction of large-scale tires. The main cause of the destruction of tires is heating of rubber causing the increase of pressure of injected gas and change of properties of tire material. Apart from friction processes and rubber deformation causing heating of wheels, the temperature of tires can increase when affected by external heat sources. At coal mines, sources of auto-ignition of fossil fuels often located along the road shoulders and sometimes on the road surface can be additional sources of heat for the vehicles. According to the calculations, the increase in tire pressure does not depend on the type of gas injected. The temperature rise in tires, however, is significantly affected by the specific heat capacity and the density of the gas used. According to the conducted studies, carbon dioxide is a more effective gas compared with air or nitrogen. With a certain amount of heat emitted in the tire, air or nitrogen heats up from 0 to 100 °С, while the temperature of carbon dioxide will increase only to 72 °С. Due to heating, the air and nitrogen pressure in the tires will increase from 6 to 8.2 atm, whereas carbon dioxide pressure will increase only to 7.5 atm. Unlike air, carbon dioxide is not involved in the combustion and oxidation of heated rubber. Methane and its homologs are even more effective. For example, propane injected into tires, when emitting the same amount of heat, will heat up from 0 only to 28 °С, and its pressure will increase from 6 to 6.6 atm. The combustion of these hydrocarbons can be prevented by using inhibitors. Thus, adding 2–3 % of freons will make these gases non-flammable and explosion-proof.

The effect of leakage on pressure loss of rotary regenerative heat exchangers

The pressure loss of the rotary exchanger is an important parameter that affects the energy consumption. Based on the literature review, the available correlations for calculating the pressure loss of rotary regenerative heat exchangers are presented in the article. The article presents extensive experimental research of rotary regenerative exchangers with different wheel geometries. A total of nine exchangers with eight different heat wheel geometries were investigated. The experiment was divided into two tasks concerning the pressure loss of the wheel channel and the total pressure loss of the built-in exchanger. The results of both approaches show differences that are caused by the leakage of rotary exchangers, which is their natural property. Based on the results of the experiment, correlations were proposed for determining the coefficient of friction in a channel in the shape of a sinusoid and a correlation for calculating the total pressure loss of the built-in rotary exchanger. The presented correlations have been experimentally verified and can be applied with a sufficient accuracy of ±5%. The new correlations were compared with the published results. The article discusses the effect of leakage of exchangers equipped with a labyrinth seal. Based on the experimental investigation, it was found that the leakage of the examined exchangers varies in a wide range of 1 to 4% and depends on the quality of the exchanger construction.

Analysis on the Quenching Deformation Characteristics of Light Cast Aluminum Alloy Wheels and Their Control Strategies

The purpose of this paper is to develop a new technology for controlling the quenching deformation of light cast aluminum alloy wheels. First, based on the existing wheel heat treatment process, a gas–liquid–solid multi-phase flow coupling model was established through the ANSYS Workbench platform to analyze the gas–liquid phase change, heat exchange on wheel surface and quenching deformation characteristics during the process of wheel immersion into the water. The results show that heat exchange characteristics of the wheel surface are comprehensively affected by wheel structure, quenching fluid flow field and gas–liquid phase transition. There are a lot of non-uniform heat exchange areas in the outer rim, spoke area and center area, which affect the overall deformation characteristics. Affected by spoke structure, the maximum deformation occurs at the outer and inner rim end faces farthest away from the wheel. Based on the above research, this paper independently develops a new deformation control strategy of spray and water immersion composite step process. Through spraying, the influence of spoke structural stiffness on the overall deformation characteristics of the wheel is effectively reduced, and the wheel deformation control is realized by meeting the mechanical properties of the wheel, with the maximum deformation reduction of 39.2%. This study provides a new option for the integrated control of deformation and mechanical properties of aluminum alloy wheels.

Features of restoring the rolling profile of wheels coming into turning during repair

The main objective of the performed studies was to improve the durability and operability of railroad wheels and make lower the costs of acquiring new ones by means of an innovative technology development for wheel profile rehabilitation and further restoration of physical and mechanical properties of the rim metal and improvement its structure. The information consists the facts about the nature of wheel pairs damage in operation, machine-tool equipment and cutting tools, used to restore the surface, based on the analysis of which a new rational technology for repair of wheel pairs on the rolling surface profile with subsequent restoration of the original operational properties is collected. A new method of wheel rolling surface profile restoration has been developed, which includes highperformance plunge grinding and subsequent induction heating (thermocycling), resulting in the formation of structures that lead to increasing of hardness and formation of compressive stresses, which has a positive effect on the efficiency of wheel rolling surface operation. This increases wheel life and safe operation of rail rolling stock. The implementation of the wheel profile recovery method with the help of highperformance plunge grinding and induction heating of wheels will lead to increased efficiency of railway rolling stock and reduce the need for the purchase of new wheelsets.

Performance Analysis of Evaporation and Heat Wheel-Based Building Air Conditioning Systems

Abstract Air conditioning in composite weather is relatively more challenging and also carries importance as it resembles conditions of hot-dry, cold, and warm-humid climates. Bifurcation of cooling and ventilation tasks happens to be one of the attractive techniques to design energy-efficient air-conditioning systems. It deals with the concept of providing a dedicated outdoor air system (DOAS) in conjunction with the air-conditioning unit. This study establishes the electrical energy consumption behavior of a building air-conditioning unit when modifications are done along the air pathway of the desiccant-integrated DOAS. For a 511 m2 building situated in composite weather, simulations in energyplus are carried out after necessary validations with the available standards. Here, two modes are discussed: in the first one, an indirect evaporation cooler (IEC)-based system is analyzed, while in the second mode, a heat wheel has been studied. For regeneration, a solar collector and supplementary electrical heater are provided. For the dynamic pattern of site environmental conditions, variations of room air temperature, humidity, thermal load, electricity, thermal energy, and solar fraction have been studied. Current analysis demonstrates that approximately 2994 kWh of the total thermal energy delivered by solar collector and supplementary electrical heater system can be saved through heat wheel instead of IEC. The usage of a heat wheel in the airflow pathway of the desiccant-integrated DOAS can offer energy savings up to 5.04% of the electrical energy with respect to IEC-integrated DOAS. Furthermore, the suggested design delivers a higher solar fraction.

Gauge widening failures of wagon wheels in Indian Railways: Finite element modeling and observed statistics

There were many gauge widening cases identified in wagon wheels of Indian Railways during the past decade, but no investigation was conducted to analyse the failures. The present work aims to investigate the main cause of failures in wagon wheels due to gauge widening. A train running model is used to estimate heat generation at wheel and brake block interface. A finite element model is used to estimate temperature and stress state in the wheel during heat treatment, wheel and axle fitment, and braking. Heat partition between brake blocks and wheel is considered for the analysis. Further, heat losses to the environment because of convection and radiation are also incorporated in the model. The wheel gauge reduces during the braking process and the permanent wheel gauge increases during the cooling process. Permanent wheel gauge increases with non-uniformity in braking and a higher frequency of braking.

Effect of steering wheel heating system on hand thermal sensation

Effect of steering wheel heating system on hand thermal sensation

The use of machine learning to determine moisture recovery in a heat wheel and its impact on indoor moisture

Balanced mechanical ventilation equipped with heat recovery has been widely adopted in cold climates to ensure an acceptable indoor environment in energy-efficient buildings. An acknowledged trend to achieve more energy savings is to increase the temperature efficiency of heat recovery. As one of the efficient heat recovery technologies extensively used in Nordic countries, the rotary non-hygroscopic heat wheel yields high-temperature efficiency with low frosting risk. Due to the increasing temperature efficiency to comply with the tightened energy performance requirements, moisture recovery in heat wheels may occur more frequently and intensively. Moisture transfer from the extracted air to the supply air in non-hygroscopic heat wheels is not well known and scarcely studied. The impact of the resulting moisture recovery in heat wheels on indoor humidity is unclear.This study uses machine learning algorithms to model and predict moisture recovery in a heat wheel. The effects of this moisture recovery on the supply and extract air, and indoor moisture levels in different rooms are analytically assessed for a selected single family house. The highest moisture recovery efficiency can reach 68%, and the yearly average value is 19% for the heat wheel in this study. For the specific studied single-family house, the heat wheel's moisture recovery introduces higher peaks in the supply air, bedrooms and living room. In general, the presence of moisture recovery in the heat wheel has a relatively limited effect on indoor humidity levels for a well-insulated and airtight house with the least amount of moisture generation scheme.

Development of a 2D finite element model for the investigation of the tread braked railway wheels thermo-mechanical behaviour

The main drawback of tread braking is the rail wheel heating due to friction sliding. Thermal stresses and strains can lead to wheel surface damages while at the same time fast cooling from high temperature can cause microstructural changes, with possible local formation of brittle martensite. Nowadays, the investigation of the wheel and shoe thermomechanical interaction is typically performed using finite element (FE) codes. The paper shows the development, implementation and preliminary validation of a 2D plane FE model for the calculation of the thermal field produced in a tread braked wheel due to drag and stop braking operations. The model includes a structural contact module for the static calculation of the normal and tangential contact pressure at the wheel-shoe interface and a thermal transient module, which computes the wheel temperature considering the friction heat flux and the cooling due to air convection and rail chill.

Analysis of supplemental dehumidification for increased energy efficiency of shoulder seasons based on climate change predictions in Austin Texas

This research project compared a standard vapor compression system and a standard desiccant dehumidification system with heat wheel to determine if there was some potential energy savings for “shoulder season” hours in Austin Texas. “Shoulder season” hours as defined in the paper are hours during which the dry bulb temperature falls within the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) comfort bound but the humidity is above the comfortable humidity point. These hours are normally addressed with vapor compression systems which dehumidify by cooling the air under the comfort setpoint to dehumidify, which is wasteful of energy. The study found that for these shoulder season hours a desiccant dehumidification system was around 4.5 times more energy efficient at reaching comfort setpoints if free heating was used for drying the desiccant.

주기적으로 작동하는 평행류 열교환기의 해석해와 그 응용

The objective of this study is to present an analytical model for a parallel-flow rotary wheel heat exchanger. The model is based on mathematical solution for an ideal parallel-flow heat exchanger with a periodic inlet temperature condition. Air and wheel matrix temperatures are given in an infinite series of the product of trigonometric and exponential functions. An analytical expression is also presented for the effectiveness of the heat exchanger, which has been validated using literature and numerical data. The model is confirmed to give an exact result when the NTU ratio between hot and cold region is unity. It tends to give a higher error for smaller heat capacity rate ratio as it deviates from the unity. Ranges of parameters are presented with distribution of the maximum absolute error. This study shows that the model is applicable to cross-flow heat exchangers when the split ratio approaches zero.

Development of rotary heat exchanger model to investigate performance with integrating controller

The heat wheel Considers one of the best heat recovery devices with very high effectiveness, which leads to great savings in energy and operating expenses. This research study a novel dynamic model of a rotary heat exchanger automatically control the temperature of outlet air despite the operating conditions are changed. The model is implemented under MATLAB/SIMULINK environment to investigate the performance of the heat wheel considering the air properties changing during the operation. The transient effect of air-flow rate, inlet air temperature and wheel rotational speed on the output temperature and effectiveness are discussed. The optimum rotational speed of a heat wheel was investigated for different operating conditions. The temperature distribution of air and matrix for one Full cycle of heat wheel were investigated. The model was validated based on data found in previously published experimental work. Results reveal that the effectiveness of the device is inversely proportional to the amount of flow, while it is directly proportional to the rotational wheel speed. The effectiveness is slightly affected by the inlet air temperature.

Improving the properties of wheeled steel during thermal repair

The purpose: to increase durability and life of railway wheels and to reduce the cost of purchasing new ones by restoring the mechanical properties of the metal rim and improving its structure. Methods: study using a multiple electron microscope and local X-ray spectral analysis of wheeled steel after induction thermocyclic processing at a high-frequency facility and in a state of delivery. Results: The structure resulting from induction thermocyclic processing - sorbit leads to the formation of compressive stresses, which has a positive effect on the efficiency of the surface of the wheel. As a result, the reliability of the wheel on accidental failures (cranks, chippings, etc.) is improved and, as a result, the safety of the operation of rolling stock is improved. Practical importance: the rational use of induction wheel heating technology will improve the efficiency of the use of rolling stock by significantly reducing the number of purchases of new wheel pairs.

Development and Experimental Validation of TRNSYS Simulation Model for Heat Wheel Operated in Air Handling Unit

Reducing energy usage to save the environment is one of the main goals for the future. The energy losses in ventilation have a huge impact on energy consumption in buildings. In this work, the energy performance of a heat recovery wheel system equipped in an air handling unit was tested year-round, and the results compared with the simulation output for the system using TRNSYS software. The selected conditioned space was the staff offices of an H&M fashion shop, located in Eger, Hungary. Temperature, relative humidity, and air velocity sensors were placed at the wheel inlet and outlet sections to record data and determine the annual energy saving. The results revealed a good agreement between the measured and simulated results.

Experimental analysis of a solar assisted desiccant-based space heating and humidification system for cold and dry climates

In the current work, an experimental analysis of a solar-assisted desiccant based heating and humidification system is performed for winter season under actual cold and dry conditions of Taxila, Pakistan. The installed setup consists of a silica-gel based desiccant wheel, a heat wheel, dual collector field of flat plate and evacuated tube collectors, and insulated storage tank. The day long measurements and assessments are reported during the months of December to February. The selected months represent wide range of cold and dry weather conditions which are applicable to different climate zones. The experimental results revealed that on average the system heating capacity, COPth, COPe, and auxiliary thermal power requirements for heating are around 5.9 kW, 1.48, 2.14 and 2.75 kW, respectively. Moreover, the solar fraction and the thermal efficiency of collector arrays are observed to be 64.75% and 40%, respectively. The uncertainties associated with humidification effectiveness, heating capacity and COPth are ±2.1%, ±5.5%, and ±7%, respectively. Finally, heating seasonal performance factor of 5 Btu/Wh is achieved. Based on the assessments, it is noted that the solar-assisted heating and humidification system is a viable solution for operation in cold and dry conditions.

ИССЛЕДОВАНИЕ ПРОЦЕССА ТЕПЛОВОГО КОНТРОЛЯ КОЛОДОЧНЫХ ТОРМОЗОВ ПОДВИЖНОГО СОСТАВА МЕТОДОМ ИМИТАЦИОННОГО МОДЕЛИРОВАНИЯ

The development of heavy speed freight train communications in the Russian Federation results in the increased thermal loading of braking system elements of rolling-stock, in particular, in shoe brakes. Taking into account the requirements of branch program documents on wheel life increase, it is evident that the further development of freight communications requires a complex application of thermal diagnostics means for auto-brake equipment of rolling-stock during a train motion. 
 The statistics shows that the fifth part of wheel pair failures is connected with thermal-mechanical damages and the situation goes on to be aggravated. In view of this hardware and software means for thermal diagnostics of shoe brakes require further improvement. The purpose of this paper is the process investigation of shoe brake thermal control by method of computer simulation and the estimate of infrared optics position impact upon control results. 
 There is considered a model for the definition of a scanning path and computation of a signal level being part of a complex simulation model of wheel thermal control. The model offered is based on the methods of solid dynamics system investigations in the basis of which there is an application of theorems on mass center motion and changes of a solid kinetic moment. 
 The model is used for finding a form and a spot area at every time moment of scanning by a solution of a problem on a dynamic spatial intersection of a wheel surface with the control area. There are considered different versions of optics orientation to an object of control for each of which for the first time there are obtained calculated thermal signals from the object under control. The analysis has shown that at the optics orientation to wheels from the outside a wheel tread appears to be in the control area that allows defining a maximum temperature of a wheel. But at the realization of emergency brake application a sharp short-time temperature increase of a tread is possible which indicates an improper operation of a brake unit. 
 The optics orientation to a wheel from its inner side allows excluding false alarm indices at emergency brake application. The correctness of the results shown in the paper is confirmed by convergence with the results of wheel heating monitoring and environmental tests of experimental complexes of thermal control means of shoe brakes.

A case study of gear wheel material and heat treatment effect on gearbox strength calculation

The paper is focused on the influence of gearing material and thermal or chemical-thermal processing of wheels on the results of the strength calculation carried out in accordance to the standard, in particular on the safety factor. This effect is examined on a gearbox that was part of the steel coil production line in the integrated steel plant. Due to changes in production, the load on the gears increased. Thus, the result of this work is the selection of new materials for the two-speed gearbox and their heat treatment to meet the safety conditions of the gearing mechanism without changing the geometrical parameters of the gearbox.

Energy Performance Investigation of a Direct Expansion Ventilation Cooling System with a Heat Wheel

Climate change is continuously bringing hotter summers and because of this fact, the use of air-conditioning systems is also extending in European countries. To reduce the energy demand and consumption of these systems, it is particularly significant to identify further technical solutions for direct cooling. In this research work, a field study is carried out on the cooling energy performance of an existing, operating ventilation system placed on the flat roof of a shopping center, located in the city of Eger in Hungary. The running system supplies cooled air to the back office and storage area of a shop and includes an air-to-air rotary heat wheel, a mixing box element, and a direct expansion cooling coil connected to a variable refrigerant volume outdoor unit. The objective of the study was to investigate the thermal behavior of each component separately, in order to make clear scientific conclusions from the point of view of energy consumption. Moreover, the carbon dioxide cross-contamination in the heat wheel was also analyzed, which is the major drawback of this type heat recovery unit. To achieve this, an electricity energy meter was installed in the outdoor unit and temperature, humidity, air velocity, and carbon dioxide sensors were placed in the inlet and outlet section of each element that has an effect on the cooling process. To provide continuous data recording and remote monitoring of air handling parameters and energy consumption of the system, a network monitor interface was developed by building management system-based software. The energy impact of the heat wheel resulted in a 624 kWh energy saving and 25.1% energy saving rate for the electric energy consumption of the outdoor unit during the whole cooling period, compared to the system without heat wheel operation. The scale of CO2 cross-contamination in the heat wheel was evaluated as an average value of 16.4%, considering the whole cooling season.

Performance characteristics of a solar desiccant/M-cycle air-conditioning system for the buildings in hot and humid areas

This paper presents a transient investigation on the performance of a solar desiccant cooling system integrated with a counter flow Maisotsenko cycle heat and mass exchanger as an air-conditioning system for the buildings in hot and humid areas. The investigation is performed using TRNSYS software linked with a MALAB code for simulating the Maisotsenko cycle. The developed model is validated using the experimental data with the highest deviation of 4.5%. Three different mixtures of the indoor and outdoor air [100%:0% (RA1), 75%:25% (RA2) and 50%:50% (RA3)] are considered as the return air. It is found that the COP and the cooling capacity of the system decrease by the more fraction of outdoor air in the return air, whereas the supply and regeneration temperatures increase. The findings show that the solar fraction in the case of RA1 is approximately half that in the case of RA3. Based on the results of the sensitivity analysis of the system with 100% indoor air as return air, the system EER increases slightly from 0.78 to 0.82 by increasing the collector area from 16 to 25 m2. However, the system COP has a reducing trend by the collector area. Both COP and EER are enhanced by the heat wheel efficiency, because the more sensible load from the supply air is transferred to the return air.