Heat Wheel Research Articles

Team Arrangement Heuristic Algorithm (TAHA): Theory and application

In this research study a novel human inspired optimization algorithm namely Team Arrangement Heuristic Algorithm (TAHA) is proposed, based on the pyramidal structure of a company and also the activities of each member in the company. It is assumed that in a company three groups of members do activities, which are the CEO, directors and employees. The right arrangement of these members and also connection between them will lead the company to the best situation where, the best project will be handled by the company, with the best members and the project will be precisely finished at its dead line with a high quality. The performance of the proposed algorithm has been evaluated with popular unimodal and multimodal functions. Also CEC2005 benchmark functions are used as a challenging problems. Seven popular optimization algorithms namely, particle swarm optimization (PSO), cuckoo search (CS), fire fly algorithm (FA), flower pollination algorithm (FPA), krill herd (KH), grey wolf optimizer (GWO) and gravitation search algorithm (GSA) are used for the purpose of comparison. Two real case engineering problems, which are heat wheel optimization problem and horizontal axis tidal current turbine problem, are solved using TAHA and other mentioned algorithms. The results indicated that TAHA outperforms other algorithms in several cases and it has a great performance in solving complicated optimization problems.

Study on material removal mechanism of electrochemical deep grinding

Deep grinding, such as creep-feed grinding and high efficiency deep grinding, offers the possibility of high process efficiency. However, deep grinding is also suffering from grinding heat and grinding wheel wear, resulting in serious surface damage and precision error. Hybrid machining process is generally regarded as effective way to improve the machining performances. Electrochemical machining (ECM) is an anodic electrochemical dissolution process that can effectively remove materials without limitations in terms of the mechanical properties of the alloys. Therefore, this paper attempts to combine deep grinding with ECM process, which can be named electrochemical deep grinding (ECDG). During ECDG process, mechanical grinding and ECM process are simultaneously applied on the anode workpiece. With the aid of high-speed ECM process, the cut-depth is greatly increased without damaging the workpiece. The feed rate and machining stability are also further improved by scraping the electrolyte product and insoluble components. The removal mechanism of anode material during ECDG process was studied through experiments in detail. Based the detailed analysis of material removal phenomenon, a qualitative model of material removal mechanism of ECDG was established. This research provides valuable insights into the material removal mechanism and the dependence of MRR and surface quality on machining conditions in the hybrid process of ECM and deep grinding.

Mobilization of Water Cycle and Its Persian Air Wheel Heat Pump to Overcome Global Heating and Its Resulting Terrible Environmental Problems

The earth Globe and its all living inhabitants, are under extremely sever and perishing multipronged attack from the Global Heating and its team, the Greenhouse Gasses (GHG), Environmental Pollution, and Stratospheric Ozone Layer Depletion and hence Penetration of Solar Ultraviolet Radiations. The major and mother of the gang of all these dragons is Global Heating. This is mainly rising up due to continuously increasing heat input by the mankind ac-tivities like burning of the fossil fuels, explosives based warfare and jungle fires etc., on one hand and continuously decreasing its outflow on the other hand through Pollution and GHG thus evolved and through some other human contributing activities not yet exposed. To restore the climate safe status, the mankind has not only to limit heat input by strict control on all direct and indi-rect contributors, but also has to accelerate the heat outflow through mobilization of God Gifted Water Evaporation and Precipitationcycle (WEPC) and its catalyst, the Persian Air Wheel Heat Pump (PAWHP). Their working mechanism and capability to challenge Global Heating are elaborated in this work. The WEPC has about 75% share in Global Heat export to the outer space, but in place of its promotion through utilizing the available opportuni-ties, the mankind has ignorantly rolled hurdles in its natural working. All the stakeholders, especially the scientific community, are requested to urge the world leaders to mobilize WEPC and PAWHP wherever possible through United Nations Organization (UNO) and impose strict control on heat and pol-lution input and promote heat and pollution free means for energy generation.

Enhanced thermodynamic assessments of the novel desiccant air cooling system for sustainable energy future

In this study, a newly developed desiccant air cooling system with desiccant wheel, sensible heat wheel and evaporative air cooler is assessed. The main purpose of the study is to investigate the developed desiccant air cooling system and compare its performance with the previous studies to show reliability of the developed system. The energy, exergy and sustainability analyses methods are used to assess the system. The data are obtained at 35 °C and 101.3 kPa environment condition. According to the exergy analysis, this system can be largely improved. The electrically and thermally driven energy coefficient of performance of the overall system (6.71 and 0.77) are higher than the corresponding exergy coefficient of performance (0.198 and 0.463). Energy coefficient of performance shows that the performance of the overall system is high, however electrically driven exergy coefficient of performance shows that some modifications can be realized in order to improve the final performance of the system. Among the components, desiccant wheel should be improved, because its exergy destruction ratio is 42.87% and the exergy efficiency is about 38.35%. On the other hand, sensible heat wheel exergy destruction ratio is computed as 10.35%, and its exergy efficiency is determined to be 57.69%. Among the components, desiccant wheel has less sustainability than others considering a combination work together. The effectiveness of the components from maximum to minimum are as sensible heat wheel, regenerative evaporative cooler and desiccant wheel, respectively. For better effectiveness, the component devices should be working around similar high level. So, the urgent improvements for the devices are in the order of desiccant wheel, regenerative evaporative cooler and sensible heat wheel, respectively.

Flow Regime Algorithm (FRA): a physics-based meta-heuristics algorithm

In this research study, a physics-based optimization algorithm, namely Flow Regime Algorithm (FRA) is proposed. The main sources of inspiration are classical fluid mechanics and flow regimes. The flow regime usually is being divided into two categories which are laminar and turbulent flows. Reynolds number is the parameter which defines that the flow regime is laminar or turbulent. In this research study, a similar number to Reynolds has been defined which indicates the search type (global or local) of the algorithm and is called search type factor. For the purpose of developing the local and global searches equations, the concept of boundary layer in fluid mechanics has been used. The performance of the proposed algorithm has been evaluated using 26 benchmark functions and has been compared with seven popular and well-known algorithms which are simulated annealing, particle swarm optimization, firefly algorithm, cuckoo search, flower pollination algorithm, krill herd and monarch butterfly. Finally, the heat wheel optimization problem and horizontal axis marine current turbine (tidal turbine) problem, which are real-case engineering problems, have been solved using FRA. The results indicated that FRA can be a great candidate in solving complex engineering problems.

Simulation of wheel heating when drum braking

Application of heating control systems is rational for effective prevention of thermal-mechanical damages of the wheels and brake shoes of rolling stock. These systems enable to perform diagnosis of brake equipment elements and to evaluate the effectiveness of drum braking process in terms of wheel heating. The present study aims to assess wheel heating when drum braking and to define the most informative zones and threshold control values for heating control systems. Heating evaluation is conducted using finite element method under different braking modes. Research results are given as heating patterns in solid-rolled wheel of freight car; the influence of the air distributor mode on the wheel heating is considered, the most informative zones for heating control are identified.

Free cooling technologies for data centers: energy saving mechanism and applications

Air conditioning and cooling systems account for about 40 % of total electricity usage in data centers. Free cooling is a novel and promising technology that can decrease the load ratio of electrical chiller and save cooling energy consumption accordingly, through making full use of natural free cooling source. In this paper, four typical free cooling systems are analyzed and compared, to show their mechanisms, main features, energy saving effects and applicable situations respectively. (1) Direct fresh air cooling is of the highest free cooling potential. However, it is hard to meet indoor air quality demand due to the indoor-outdoor air mixing. (2) Rotating wheel heat exchanger can be used for indirect free cooling, since indoor and outdoor air flow in different paths for heat exchange. While its power usage effectiveness (PUE) increases inevitably under the same climatic conditions. (3) Heat pipe can be integrated with rack back plate to enhance heat transfer with free cooling sources. Its cooling efficiency can increase by 3-5 times compared to traditional heat exchangers. (4) In water-based free cooling system, a heat exchanger is installed in parallel with electrical chiller and the system can work under three modes according to different outdoor temperature. Increasing the load ratio of free cooling can decrease PUE and save electricity usage. In practical applications, the cooling system design for data centers depends on various factors, such as indoor air quality requirement, local climatic conditions, energy saving demands, room space, capital investment and operation costs.

Energy performance of GCC-specification LCC optimized dedicated outdoor air system configurations coupled to an air-cooled outdoor unit

Direct expansion (DX) dedicated outdoor air system is shown to be a cost-effective energy efficient complement to ductless variable refrigerant flow and radiant cooling systems by providing conditioned ventilation air at the required set point temperature and relative humidity in an energy efficient manner. We compare five balanced flow dedicated outdoor air system configurations under typical office/lab ventilation loads coupled to an air-cooled outdoor unit for 24 Gulf Cooperation Council (GCC) locations representing GCC climates. All configurations use an enthalpy recovery wheel (ERW) to remove heat and moisture from intake air—before it reaches the active DX dehumidification element—by passive heat and mass transfer to the exhaust stream. It is found that of two run-around heat exchanger configurations, using a rotary heat wheel across the evaporator is a more efficient configuration than placing the heat wheel (HW) between the supply and return air streams. Furthermore, adding a subcooling coil for reheat in parallel to the HW results in higher efficiency than adding the coil in series with the HW. The Life cycle cost optimized ERW and HW effectiveness for the configuration with HW between supply and return air was found to be 0.86 while the ranges for run-around HW configurations with subcooling/reheat were found to be 0.8–0.85 for ERW and 0.74-0.82 for HW in GCC climates with significant dehumidification loads. Thus, the evaporator run-around HW reduces the volume, mass and cost of the DOAS unit while providing higher overall efficiency.

Theoretical Prediction of Longitudinal Heat Conduction Effects on the Efficiency of the Heat Wheel used for Ventilation in Powerhouse Building “Kjørbo” in Norway

The present study investigates effects of longitudinal heat conduction (LHC) on the heat recovery effectiveness of the heat wheel in the Powerhouse building “Kjørbo”. The effects LHC which are usually ignored in the heat wheel design play a relatively significant role in the heat wheel with high temperature efficiency and short depth in flow direction. The correlation developed by Shah, Kays and London is applied to predict the temperature efficiency and to investigate the impacts of the LHC. Good agreements have been observed between the theoretical predictions obtained from the correlation and experimental data collected from the field test at “Kjørbo”. The influence of the depth of the heat wheel, the airflow rates on the LHC and temperature efficiency were analysed. It was found that the heat wheel has difficulty to achieve a high temperature efficiency (85%) due to the effects of LHC. There is an optimal depth design for heat wheel in the flow direction to recovery maximum thermal energy with low pressure loss with considering the LHC effects. The present study provides preliminary analysis to optimize the heat wheel design and operation with the LHC being taken into account.

Numerical investigation of a heat wheel performance used for enthalpy recovery applications

Numerical investigation of a heat wheel performance used for enthalpy recovery applications

Modernization of Railroad Wheel Manufacturing Technology at Evraz Ntmk

Results are provided for a study of the production process for manufacturing railroad wheels aimed at a reduction in metal consumption coefficient, material and energy expenditure, an increase in stability of quality characteristics, and wheel life. At the EVRAZ NTMK combine, comprehensive broad scale work is carried out, and new engineering solutions are found and introduced for converter processing and steel extra-furnace treatment for preparation of an ingot in a CBCM, and new production schemes are assimilated for deformation treatment during stamping, rolling, bending, straightening, and wheel sizing. As a result of combined operation of upsetting, flattening, and sizing of a billet in the preliminary stamping stage and also the use of a method for self-centering of a stamping in final forming dies, an increase is provided in the precision of a rough wheel and a reduction in original billet weight. A high level of automation and metrological provision for the production process of the pressing and rolling line, make it possible to accomplish adjustment of parameters in a real time regime and to minimize scrap. Stiffening of specifications with respect to wheel heating temperature for hardening and use of rational cooling rates for the wheel rim in quenching benches facilitates assimilation of production of hard (320 HB) and especially hard (350 HB) wheels with stable qualities. Operating properties of railroad wheels improve by a factor of 1.5, including due to introduction of complete profile machining of a wheel, shot-peening strengthening of a disk, and toughening ultrasonic and magnetic luminescence monitoring for quality.

Effect of Spun Velocities and Composition on the Microstructure and Transformation Temperatures of TiNi Shape Memory Ribbons

Ti‒50.13Ni and Ti‒49.62Ni (at.%) shape memory alloy ribbons were fabricated by melt-spinning method at different circumferential wheel velocities. The effects of wheel velocity, chemical composition and heat treatments on microstructure and Transformation temperature were investigated. Differences in wheel velocity led to differences in cooling rate and sample dimension, as well as in phase transformation temperatures. Two heat treatment conditions were studied, 350°C for 1h and 350°C for 5h. In the samples produced at high wheel velocity and heat-treated at 350°C for 5h, nanosized Ti-rich precipitates were observed in both chemical compositions. Cross-sectional microstructure was studied by optical microscopy; SEM was used to study the nanometric grains and nano precipitation. The transformation temperatures were analyzed by DSC.

Investigation on Heat Transfer Performance of Heat Pipe Grinding Wheel in Dry Grinding

The use of fluid in grinding enhances heat exchange at the contact zone and reduces grinding temperature. However, the massive use of fluid can cause negative influences on environment and machining cost. In this paper, a novel method of reducing grinding temperature based on heat pipe technology is proposed. One new heat pipe grinding wheel and its heat transfer principle are briefly introduced. A heat transfer mathematical model is established to calculate equivalent thermal conductivity of heat pipe grinding wheel. Compared with the wheel without heat pipe, heat transfer effect of heat pipe grinding wheel is presented, and the influences of heat flux input, cooling condition, wheel speed, and liquid film thickness on heat transfer performance are investigated. Furthermore, dry grinding experiments with two different wheels are conducted to verify the cooling effectiveness on grinding temperature. The results show that thermal conductivity of the wheel with heat pipe can be greatly improved compared to the one without heat pipe; heat transfer performance of heat pipe grinding wheel can change with different grinding conditions; meanwhile, grinding temperatures can be significantly decreased by 50% in dry grinding compared with the wheel without heat pipe.

Optimizing Control of Dedicated Outdoor Air Systems with Energy Recovery in Commercial Buildings

AbstractDedicated outdoor air systems (DOASs) with energy recovery ventilators (ERVs) are increasingly popular in new buildings and have the potential to greatly reduce building energy consumption through elimination of zone-level summer reheat and free preconditioning of outdoor ventilation air through energy recovery with building exhaust air, often using an enthalpy wheel heat exchanger. In practice, many of these systems, however, are run suboptimally or are designed with complex and counterintuitive configurations that require detailed engineering analysis to understand optimal control sequences. Three real-world case studies from commercial building retuning are presented where control deficiencies in DOASs with ERVs led to excess energy consumption. An analysis of the potential energy savings from correcting these deficiencies as well as a discussion of how each analysis was performed during the retuning audit is included. Energy savings can vary significantly based on the climate and the baseline ...

Effect of Spun Velocities and Composition on the R‒phase and Thermomechanical Behavior in Ti‒Ni Ribbons Electrically Heated

This work deals with structural, electrical and mechanical characterization of Ti‒50.13Ni and Ti‒49.62Ni (at.%) shape memory alloys (SMAs) fabricated at different circumferential wheel velocities. The effect of wheel velocity, chemical composition and heat treatments are investigated. The characterization of crystallographic phases of the Ti‒Ni ribbons was carried out using X-ray diffraction. Electrical resistance variations as function of temperature (∆R/R %) were analyzed using a non-commercial technique, which consists in a thermal-adjustable bath apparatus revealing the temperatures of B2→R→B19´ two stage transformation, whereby the presence of R‒phase can be definitively confirmed. The Stress-Assisted Two-Way Memory Effect was measured by an own designed apparatus with an Linear Variable Differential Transformer captor and a current controlled heating, and results indicate that the as-spun condition, promotes the Stress-Assisted Two-Way Memory Effect. On the other hand, increments in Ni content tend to decrease transformation temperatures and high wheel velocities help to the R‒phase formation.

Determination of air-to-air heat wheel sensible effectiveness using temperature step change data

The determination of the effectiveness of large heat wheels using standard measured data and test conditions can be very expensive and time consuming. The main contribution of this paper is that it tests heat wheel components rather than the wheel itself. In addition, this paper deals directly with the question of what accuracy can be achieved for the determination of sensible energy effectiveness by using a transient step change method for the exchanger matrix materials in a test cell. In this study, the sensible effectiveness of heat wheels is predicted by performing a number of cyclic and single step change transient experiments on a parallel-plate heat exchanger. A new experimental facility is developed to cause a step change for the inlet air temperature of the exchanger. In the cyclic tests, the heat exchanger is exposed to a periodic inlet temperature steps; afterward, the sensible effectiveness of parallel-flow and counter-flow heat wheel, comprised of the same material as parallel-plate exchanger, is determined using the obtained temperature profiles. It is find that this method can be used to determine the sensible effectiveness of parallel-flow heat wheel. However, the high uncertainty found in the sensible effectiveness of counter-flow heat wheel, ±32%, makes the results unreliable. In the single step-change test, a time constant is assigned to the exchanger response when it is subjected to a step change in inlet temperature. The time constant is obtained by fitting the experimental data to a first order exponential time response curve. An analytical solution posits that the effectiveness of the heat wheel depends only on the product of the time constant and the wheel angular speed, or angle ratio. Comparing values of the sensible effectiveness calculated through available empirical correlations and the ones obtained by single step change experiment showed less than 3% difference in results when the heat capacity rate ratio is greater than 5. It is concluded that due to simplicity, accuracy, and low cost of the single step change experiments, it is the preferred method to determine the effectiveness of heat wheels operating at a specified rotary speeds, provided the flow channel geometries and Reynolds numbers for both the wheel and the small-scale test cell.

Modelling of a rotary desiccant wheel: Numerical validation of a Variable Properties Model

Desiccant cooling systems have been used since the early '30s, mainly for industrial applications in which significant economic benefits could be achieved from an accurate humidity control. The core unit of a desiccant cooling system is the desiccant wheel device, the performances of which determine size and cost of the whole system. As a result, having a good desiccant wheel mathematical model can be an useful tool to optimize the operation of the device, as well as a valuable aid in the design phase.In this paper a one-dimensional coupled heat and mass transfer desiccant wheel model was developed, taking into account the dependence of thermodynamic and transport properties of humid air with temperature (Variable Properties Model, VPM). The model has been validated using both literature and experimental data in terms of temperature and humidity profiles at the exit of the wheel, dehumidification effectiveness, dehumidification coefficient of performance and sensible energy ratio.Compared to the traditional models, significant improvements in the agreement between numerical predictions and experimental data have been observed. It was found that mean relative error between measured and VPM calculated data were always significantly lower than those between the same experimental data and values calculated according to widespread literature models which consider moist air properties constant with temperature; as a consequence, it can be inferred that neglecting variations of moist air properties with temperature leads to unacceptably low accuracy variables estimation.

Design Optimization of Heat Wheels for Energy Recovery in HVAC Systems

Air to air heat exchangers play a crucial role in mechanical ventilation equipment, due to the potential primary energy savings both in case of refurbishment of existing buildings or in case of new ones. In particular, interest in heat wheels is increasing due to their low pressure drop and high effectiveness. In this paper a detailed optimization of design parameters of heat wheels is performed in order to maximize sensible effectiveness and to minimize pressure drop. The analysis is carried out through a one dimensional lumped parameters heat wheel model, which solves heat and mass transfer equations, and through appropriate correlations to estimate pressure drop. Simulation results have been compared with experimental data of a heat wheel tested in specific facilities, and good agreement is attained. The device optimization is performed through the variation of main design parameters, such as heat wheel length, channel base, height and thickness and for different operating conditions, namely the air face velocity and the revolution speed. It is shown that the best configurations are achieved with small channel thickness and, depending on the required sensible effectiveness, with appropriate values of wheel length and channel base and height.

Effect of grinding-induced cyclic heating on the hardened layer generation in the plunge grinding of a cylindrical component

This paper discusses the effects of the grinding-induced cyclic heating on the properties of the hardened layer in a plunge cylindrical grinding process on the high strength steel EN26. It was found that a multi-pass grinding brings about a uniform and continuous hardened layer along the circumference of the cylindrical workpiece. An increase of the number of grinding passes, leads to a thicker layer of hardening, a larger compressive residual stress and a deeper plastic deformation zone. Within the plastic deformation zone, the martensitic grains are refined by the thermo-mechanical loading, giving rise to a hardness of 12.5% higher than that from a conventional martensitic transformation. The coupled effects of heat accumulation and wheel wear in the multi-pass grinding are the main causes for the thickening of the hardened layer. A too small infeed per workpiece revolution would result in insufficient grinding heat, and in turn, bring about an undesirable tempered hardened layer and a reduction of its hardness.

Microstructure and mechanical properties of twin-wire arc sprayed Ni-Al composite coatings on 6061-T6 aluminum alloy sheet

We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coatings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear behavior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treatment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers microhardness of NiAl and Ni3Al intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth exponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550°C, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.