Thermal Wheel Research Articles

Multi-objective optimization for surface grinding process using a hybrid particle swarm optimization algorithm

Optimization for the surface grinding process is a problem with high complexity and nonlinearity. Hence, evolutionary algorithms are needed to apply to get the optimum solution of the problem instead of the traditional optimization algorithms. In this work, a hybrid particle swarm optimization (HPSO) algorithm which combines the dynamic neighborhood particle swarm optimization (DN-PSO) algorithm with the strategy of mutation considering constraints is presented to handle multi-objective optimization for surface grinding process. Such four process parameters as wheel speed, workpiece speed, depth of dressing, and lead of dressing are considered as the variables for optimization, and the following three objectives such as production cost, production rate, and surface roughness are used in a multi-objective function model with a weighted approach. Meanwhile, the constraints of thermal damage, wheel wear, and machine tool stiffness are considered. Computational experiments are conducted on cases of both rough grinding and finish grinding, and comparison results with the previously published results obtained by using other optimization techniques shows the efficiency of the proposed algorithm.

Research on the Distribution of Grains in the Grinding Process

Grinding of metals is a complex material removal operation involving cutting, ploughing, and rubbing depending on the extent of interaction between the abrasive grains and the workmaterial under the conditions of grinding. In this investigation, various parameters of the process including the number of abrasive grains in actual contact, the number of actual cutting grains per unit area for a given depth of wheel indentation, the minimum diameter of the contacting and cutting grains, the probability of active contacting grains and cutting grains were determined analytically. The analytical work was proved to be practicable by the means of measuring grinding temperature. Research results enable the use of actual number of contacting and cutting grains in the grinding wheel for thermal distribution and wheel wear analyses and contribute to a better understanding on the mechanics of grinding.

Thermal simulation of a pin on a rotating cylinder jacket system

In this paper specimen level measurements and finite element simulations are introduced in order to study the thermal behaviour of a pin and wheel sliding contact configuration. The pin-like specimen is processed from cast iron and models the local contact of a railway brake block and wheel tire. The sliding contact is treated in the framework of a 3 dimensional problem in order to achieve reliable results. The paper also treats with the heat partition problem by distributed heat source and moving heat source models. The results are compared to measured datas and show that the classical heat partition approach is not valid for the friction pair examined i.e. the contact. However authors determine the exact heat partition ratio by an iterative approach and give explanations on the experienced temperature differences.

Multiobjective Optimization of Grinding Process Parameters Using Particle Swarm Optimization Algorithm

Grinding is one of the very important machining operations in engineering industries. Optimization of grinding processes still remains as one of the most challenging problems because of its high complexity and non-linearity. This makes the application of traditional optimization algorithms quite limited. Hence, there is a need to apply most recent and powerful optimization techniques to get desired accuracy of optimum solution. In this paper, a recently developed nontraditional optimization technique, particle swarm optimization (PSO) algorithm is presented to find the optimal combination of process parameters of grinding process. The objectives considered in the present work are, production cost, production rate, and surface finish subjected to the constraints of thermal damage, wheel wear, and machine tool stiffness. The process variables considered for optimization are wheel speed, workpiece speed, depth of dressing, and lead of dressing. The results of the algorithm are compared with the previously published results obtained by using other traditional optimization techniques.

Grinding process parameter optimization using non-traditional optimization algorithms

Selection of machining parameters in any machining process significantly affects the production rate, quality, and cost of a component. This paper presents the multi-objective optimization of process parameters of a grinding process using various non-traditional optimization techniques such as artificial bee colony, harmony search, and simulated annealing algorithms. The objectives considered in the present work are production cost, production rate, and surface finish subjected to the constraints of thermal damage, wheel wear, and machine tool stiffness. The process variables considered for optimization are wheel speed, workpiece speed, depth of dressing, and lead of dressing. The results of the algorithms presented are compared with the previously published results obtained by using other optimization techniques.

Simulation–optimization of solar-assisted desiccant cooling system for subtropical Hong Kong

Abstract Solar cooling is a novel approach, which primarily makes use of solar energy, instead of electricity, to drive the air-conditioning systems. In this study, solar-assisted desiccant cooling system (SADCS) was designed to handle the cooling load of typical office in the subtropical Hong Kong, in which half of the building energy is consumed by the air-conditioning systems. The SADCS mainly consisted of desiccant wheel, thermal wheel, evaporative coolers, solar air collectors and gas-fired auxiliary heater, it could directly tackle both the space load and ventilation load. Since the supply air flow is same as the outdoor air flow, the SADCS has a feature of sufficient ventilation that enhances the indoor air quality. Although it is inevitable to involve the auxiliary heater for regeneration of desiccant wheel, it is possible to minimize its usage by the optimal design and control scheme of the SADCS. Through simulation–optimization approach, the SADCS can provide a satisfactory performance in the subtropical Hong Kong.

In-process force measurement for diameter control in precision cylindrical grinding

This article shows the theory and implementation of a force measurement-based approach to controlling workpiece diameter in cylindrical grinding. A simple model proposed is used to relate infeed velocity to grinding force. The model is extended to accurately control the amount of material removed in outer diameter plunge grinding given the normal force, which may be monitored in real-time. The model incorporates the key parameters, including the structural loop stiffness, the plunge infeed velocity, and the wheel and workpiece properties. However, only the infeed velocity must be explicitly known. The contribution of this work is experimental validation that the lag between infeed and stock removal can be predicted using force feedback without a priori knowledge of the grinding system. This allows very accurate diameter control (0.25 μm of nominal), even in the presence of thermal drift, wheel wear, and machine error.

Super-Efficient Mechanical Ventilation

A novel ventilation system has been installed in buildings constructed for the New Campus of the University of Nottingham. Super-efficient mechanical ventilation has been used as part of an integrated environmental strategy and operates with fan input powers below 0.5 W·l^–1·s^–1 of airflow. The complete plant was assembled from innovative low-pressure components and has exceptional performance. A key element of the design is that components of the system are bypassed when not in use. At the heart of the system is a low-velocity, high-efficiency thermal wheel. Evaporative cooling reduces summertime peak temperatures. A tracking wind-assisted exhaust cowl further reduces the dependence on fan power. The low fan power requirement is matched by a 450-m² photo-voltaic array effectively giving zero energy ventilation.

Super-Efficient Mechanical Ventilation

A novel ventilation system has been installed in build ings constructed for the New Campus of the University of Nottingham. Super-efficient mechanical ventilation has been used as part of an integrated environmental strategy and operates with fan input powers below 0.5 WI-1.S -1 of airflow. The complete plant was assem bled from innovative low-pressure components and has exceptional performance. A key element of the design is that components of the system are bypassed when not in use. At the heart of the system is a low-velocity, high- efficiency thermal wheel. Evaporative cooling reduces summertime peak temperatures. A tracking wind-as sisted exhaust cowl further reduces the dependence on fan power. The low fan power requirement is matched by a 450-m2 photo-voltaic array effectively giving zero energy ventilation.

Analysis of Grinding Temperatures by Energy Partitioning

The partitioning of heat between two sliding bodies depends strongly on the relative magnitude of the thermal characteristics of each body. Grinding with the superabrasive CBN (cubic boron nitride) gives the favourable condition of a high thermal conductivity wheel, allowing increased heat to be carried away by the grinding wheel. This reduces the temperatures experienced by the workpiece. In this paper different methods of theoretical partitioning in grinding are reviewed. The partition ratio is the proportion of the total grinding energy that enters the workpiece. The partition ratio in surface grinding was measured using a thermocouple technique. Theoretical models for predicting the partition ratio were correlated with measured results to establish the effective thermal properties of CBN and aluminium oxide abrasives. The effective thermal conductivity of CBN was found to be considerably lower than the reported theoretical value. The findings provide the basis for improved prediction of workpiece temperatures in grinding.

Modelling of the dynamics of a low-speed gas-liquid heat engine

This paper deals with the simulation model of a gas-liquid heat engine which is characterized by very low speeds (1–3 rpm) and relatively high torque. The engine operates according to the “Minto Thermal Wheel” principle. It is based on the conversion of thermal energy from the heat source, through gas expansion, into mechanical work, by means of the fall of a mass of liquid. A prototype has already been constructed showing great ability to operate at very low temperature differences between the heat source and heat sink. This makes the engine quite suitable to the utilization of low temperature heat sources such as solar energy and waste heat. On the other hand, the number of moving parts is kept to a minimum, since the piston of traditional positive displacement engines (PDE) is now replaced simply by a mass of liquid. The mathematical model consists of applying the energy equation, in its time-derivative form, to representative engine control volumes, resulting in a set of linear ordinary differential equations. Their integration provides the time variation of pressure and temperature of the working fluid. The engine performance can thus be predicted as a function of engine operating conditions and geometric characteristics. In this paper, the engine dynamics (i.e., variable angular speed) have been taken into account, as well as heat losses in the engine structure. Results and further design considerations are discussed.

Performance tests on an air-to-air thermal wheel in a swimming pool hall

The temperatures, humidities and air flow rates in the plant serving a public swimming pool hall were monitored for a period of about one year. The swimming pool hall was heated by an all fresh air system using LPHW heater batteries supplied by gas boilers. The plant included a thermal wheel heat recovery unit to transfer some of the sensible waste heat from the exhaust air to the supply air. The observed and calculated temperatures and energy savings are tabulated and conclusions are drawn as to the effectiveness of the thermal wheel and the energy savings predicted and observed.

Promise and potential of air-to-air energy recovery systems

This paper describes and discusses the principles, advantages, and disadvantages of several types of air-to-air energy recovery devices including the open and closed runaround systems, the heat pipe exchanger, the thermal wheel, and the plate exchanger. Emphasis is placed on the potential energy savings in heating and cooling equipment and fuel costs by recovering energy from exhaust air before it is thrown away. Results indicate annual energy savings up to 23% with even larger savings in the size of the heating and cooling equipment. As expected, greatest savings occur when large amounts of outside air are required for ventilation.