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heatgun_final

# heatgun_final - Parameterization Analysis Simulation of a...

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Parameterization, Analysis & Simulation of a Heat Gun Submitted by Thomas A. Bowers December 10, 2002 2.141: Modeling and Simulation of Dynamic Systems Fall 2002 Massachusetts Institute of Technology

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1 Introduction This paper discusses the dynamic analysis and simulation of a heat gun. The system consists of an electric heating coil and a universal AC electric motor that drives a centrifugal fan in order to produce airflow. A diagram of the system is shown in Figure 1. Although the system looks relatively simple there are complex interactions between electrical, mechanical, thermal, and fluid domains. + - Heating Coil Fan AC Motor Centrifugal Figure 1: Schematic of Heat Gun 2 System Model Because the system operates in four domains there are several couplers required to convert energy from one domain into energy in another domain. 2.1 Electro-mechanical Coupling The coupling between electrical and mechanical domains is the universal AC motor. A diagram of the universal motor is shown in Figure 2. Because the windings on the rotor are connected in series with windings on the two poles of the stator, this motor is able to Schematic and graph removed due to copyright considerations. See reference [1]. Figure 2: Universal Motor Wiring Diagram and τ -N Curve operate with an AC or DC power supply [1]. This allows the motor to be treated similarly to a simple DC motor, which is modeled as a linear gyrator. The motor constant, K m , can be determined experimentally by measuring the input voltage and current when driving the motor at a known speed. It is evident from part b of Figure 2 that AC operation is 1
even more linear than DC operation for this type of motor adding validity to the use of a linear gyrator. 2.2 Electro-thermal Coupling The interaction between the electrical domain and the fluid domain is a thermal coupling. To transfer energy to the fluid, the material of the electrical resistor must first heat up. The coupling is modeled as a non-conservative two-port resistor. This is due to the fact that electrical energy is converted to thermal energy, but thermal energy does not create electrical energy. The power dissipated in the resistor is equal to e 2 / R . This power is converted to thermal energy through the generation of entropy. Thermal energy is stored in the resistor, which acts as a thermal capacitor, and transferred to the air by convection. 2.3 Thermo-Fluid Coupling The thermal energy that is transferred through convection can be modeled using the HRS macro element that is presented in Brown [2]. This bond is used to model heat exchangers and allows the heater temperature to be much larger than the temperature of the fluid at the inlet or outlet port. 2.4 Mechanical-Fluid Coupling The centrifugal fan provides the coupling between mechanical and fluid domains. The geometry of the fan used in this heat gun is a forward-curved blade centrifugal blower, which is also known as a sirocco fan. As with the coupling between electrical and fluid

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