A direct expansion (DX) HVAC system is an efficient way to supply fresh and dehumidified air to a built environment. To improve the efficiency of a conventional DX system in hot and humid regions, fresh air dehumidification and conditioning systems with energy recovery measures are the key equipment to reach such a goal. To achieve this goal an integrated system is proposed. The integrated syst...

Hysteresis and nonlinearity exist in most valves that are utilized in building HVAC systems, such as in cooling or heating coil valves. The hysteresis mainly comes from the manufacturing clearance in an actuator gearbox and nonlinearity in the variation of the regulated flow with respect to control signal originates from valve design. The combination of valve hysteresis and nonlinearity poses s...

A data-driven approach for optimizing the reheat process in a variable-air-volume box is presented. Data-mining algorithms derive temporal predictive models from the reheat process data. The biobjective model formed is solved with a modified particle swarm optimization algorithm. To increase computational efficiency, two levels of non-dominated solutions are introduced while solving the optimiz...

The problem of closed-loop control during the thermoforming sheet reheat process is considered. The approach aims to improve the material distribution of a formed thermoplastic part via better sheet temperature control prior to forming. Improved control of material distribution will increase part quality and result in fewer part rejects, thereby increasing production efficiency. An in-cycle con...

The VAV Reheat Versus Active Chilled Beams & DOAS paper published in the May 2013 issue of the ASHRAE Journal covers an HVAC system design competition for a real office building at UC in Davis, California. The systems under evaluation are Active Chilled Beams with Dedicated Outdoor Air (ACB+DOAS), a Variable Air Volume system with Reheat (VAVR) and a hybrid of VAVR and ACB’s. Energy and cost mo...

Although failure of the seam weld on reheat steam piping has been an infrequent occurrence, such failure is still a major safety concern for fossil plant operations. EPRI has provided guidelines for a piping management program based on periodic inspection. More recently, EPRI has also sponsored research to develop inspection techniques to both improve the quality and reduce the cost of piping i...

This report summarizes work to examine interstage heating and cooling options for multiple reheat helium Brayton cycle power conversion system (PCS) designs. Previous work has demonstrated that thermal powers in the range of 2400 MWt can be readily derived from combining multiple single-expansion units derived from the 600-MWt, vertical shaft gas-turbine module helium reactor (GT-MHR). This PCS...

This paper deals with the application of multi-agent system concept for optimization of dynamic uncertain process. These problems are known to have a computationally demanding objective function, which could turn to be infeasible when large problems are considered. Therefore, fast approximations to the objective function are required. This paper employs bundle of intelligent systems algorithms ...

We study the cosmological gravitino production in gauge mediated supersymmetry breaking models, while properly taking into account the existence of the messenger mass scale. It is found that for sizable parameter range of the model the messenger sector contribution leads to more stringent upper bound on the reheat temperature obtained from the condition that the universe should not be overclose...