Heat Flux Modeling of Asymmetrically Heated and Cooled Thermal Stimuli

Thermal sensation is one of the most dynamic stimulus-response systems in the human body. It is relied upon for safety, comfort and general equilibrium of the human body. Thermal sensation is dependent upon many variables such as area of effected skin, rate of temperature change and location of stimulation. It has been shown that certain rates of change can intensify the sensation of heating or cooling. Conversely, sufficiently low rates of change can go undetected by the skin. As such, the thermal response system can be manipulated by the proper combination of applied hot and cold stimuli. Previous research has shown that through precise application of an asymmetrically heated and cooled thermal display, a sensation of constant cooling can be perceived. This thesis seeks to (1) explore the heat flux characteristics of the thermal display through the use of computer simulations, (2) test a hypothesis about the relationship between thermal sensation and heat flux and (3) examine modifications of the thermal display patterns with the intention of producing more intense thermal sensations. To characterize the heat flux patterns produced by the thermal display, finite element simulations, performed using commercially available software ANSYS©. Simulations are conducted on individual heating and cooling rates to examine the expected values of heat flux as temperatures approach and diverge from skin temperature. Evaluated in the cylindrical coordinate system (axial, angular and radial), the simulations showed a slight nonlinear heat flux generation at the beginning of heating and cooling, but after the initial transient period, this gave way to a strong linear generation of increasing or decreasing heat flux. Simulations were performed that represent the physical experiments implemented in pre- vious research. These simulations were done in two parts: the first examines a small subregion with finer detail on the area between heating and cooling stimuli, the second is a larger scale examination of the heat flux profile of the thermal display. Initially it was observed that directly under the thermal stimulus, in the radial direction, the heat flux was almost perfectly in-phase with the oscillation of temperature whereas between the stimuli, it was nearly 180 degrees out of phase. The heat flux in the axial and angular directions under the thermal stimulus were negligible. Additionally, between stimuli, the values were nearly 180 degrees out of phase with temperature. Additionally, it was observed that the heat flux profiles for all patterns used in the thermal display were approximately identical. From the data gathered by the simulations in conjunction with the thermal sensation data from previous research, a linear relationship is hypothesized that relates these two quantities. This relationship was then used to determine the theoretical thermal sensations of newly developed thermal display patterns in order to determine which are best suited for future physical experimentation