Browsing by Subject "Radiant heating"
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Item An experimental simulation of asymmetric radiant heating for the FMDF receiver(Texas Tech University, 1978-12) Shinn, Kim ENot availableItem Design optimization of radiant enclosures(2003) Daun, Kyle James; Howell, John R.Design problems involving radiant enclosures are encountered in many different industrial applications. Examples include the design of annealing furnaces used in materials processing, ovens that bake food or cure coated surfaces, and rapid-thermalprocessing chambers used to manufacture semiconductor wafers. In each of these applications, the objective of the design problems is to find the enclosure geometry and heater settings that produce the desired temperature and heat flux distribution over the product. Traditionally, this has been done using a forward “trialand-error” design methodology, which is a time-consuming process that results in a solution of limited quality. More recently, inverse design methodologies have been developed that require far less time than the forward methodology, and produce solutions that better satisfy the desired conditions over the product surface. It is difficult to enforce design constraints, however, which often limits the usefulness and applicability of solutions obtained by this approach. This dissertation describes several optimization methodologies that can be used to solve several types radiant enclosure design problems. In this approach, an objective function is first defined that quantifies the “goodness” of a particular design, in such a way that its minimum corresponds with the ideal design outcome. The objective function is dependent on a set of design parameters that control the enclosure configuration. Once this is done, the optimal set of design parameters is found by minimizing the objective function through nonlinear programming. Far less design time is required compared to the forward methodology, and the final solution is near-optimal. Furthermore, unlike the inverse methodology, it is possible to implement constraints by restricting the domain of the design parameters, which ensures that the solution can be easily implemented in a practical setting. Design methodologies are presented for design the heater settings and geometry of both diffuse-walled enclosures and enclosures containing surfaces with directionally dependent properties, and for solving the heater settings in problems involving transient and multimode heat transfer effects.Item Investigation of a Radiantly Heated and Cooled Office with an Integrated Desiccant Ventilation Unit(2009-05-15) Gong, XiangyangRadiant heating and cooling has a reputation of increasing the comfort level and reducing the energy consumption of buildings. The main advantages of radiant heating and cooling are low operational noise and reduced fan power cost. Radiant heating and cooling has been supplied in several forms, including floor heating, ceiling heating and cooling, radiant panels and fa?ade heating and cooling. Among them, fa?ade heating and cooling is the most recently developed system. This dissertation provides a comprehensive study of several technical issues relative to radiant heating and cooling systems that have received little attention in previous research. The following aspects are covered in this dissertation: First, a heat transfer model of mullion radiators, one type of fa?ade heating and cooling, is developed and verified by measured performance data. The simulation demonstrates that the heating or cooling capacity of mullion radiators is a semi-linear function of supply water temperature and is affected by the thermal conductive resistance of mullion tubes, the room air temperature, the supply water flow rate, and the outside air temperature. Second, the impact of the positions of radiators on energy consumption and thermal comfort is studied. This dissertation compares the heating load and comfort level as measured by uniformity of operative temperature for two different layouts of radiators in the same geometric space. The air exchange rate has been identified as an important factor which affects energy saving benefits of the radiant heating systems. Third, the infiltration and the interaction of infiltration and mechanical ventilation air to produce moisture condensation in a radiantly cooled office are examined. The infiltration of the studied office is also explored by on-site blower door measurement, by analyzing measured CO2 concentration data, and through modeling. This investigation shows the infiltration level of the studied office to range between 0.46 and 1.03 air changes per hour (ACH). Fourth, the integrated sensible heating and cooling system is simulated and compared with a single duct variable air volume (VAV) system. The results show that, at the current infiltration level, the studied sensible heating and cooling system with an integrated active desiccant ventilation unit consumes 5.6% more primary energy than a single duct VAV system; it would consumes 11.4% less primary energy when the system is integrated with a presumed passive desiccant ventilation unit.