Design Optimization of Heat Wheels for Energy Recovery in HVAC Systems

Abstract

Air to air heat exchangers play a crucial role in mechanical ventilation equipment, due to the potential primary energy savings both in case of refurbishment of existing buildings or in case of new ones. In particular, interest in heat wheels is increasing due to their low pressure drop and high effectiveness. In this paper a detailed optimization of design parameters of heat wheels is performed in order to maximize sensible effectiveness and to minimize pressure drop. The analysis is carried out through a one dimensional lumped parameters heat wheel model, which solves heat and mass transfer equations, and through appropriate correlations to estimate pressure drop. Simulation results have been compared with experimental data of a heat wheel tested in specific facilities, and good agreement is attained. The device optimization is performed through the variation of main design parameters, such as heat wheel length, channel base, height and thickness and for different operating conditions, namely the air face velocity and the revolution speed. It is shown that the best configurations are achieved with small channel thickness and, depending on the required sensible effectiveness, with appropriate values of wheel length and channel base and height. OPEN ACCESSEnergies 2014, 7 7349

Minimization of the Lifecycle Cost of a Rotary Heat Exchanger Used in Building Ventilation Systems in Cold Climates

“…The characteristics of the rotary heat exchanger are introduced by applying the function of porous material. In this case, the porosity of the material σ, the ratio between the surface area and volume A/V and the heat transfer rate h T are introduced [13]. First, the problem is approached in a stationary mode until the air velocity and temperature stabilizes while the rotor is not running.…”

“…The literature review has shown that once the rotational speed of the rotary heat exchanger reaches a certain value, there is virtually no effect on the temperature efficiency [2], [5] and [13]. The results of a large number of studies show that this value does not exceed 12 revolutions per minute.…”

“…Recovered heat and energy used in fans are defined as "conflicting objectives", and a solution is given as a Pareto optimum. In the field of air conditioning, the connection between heat transfer efficiency and pressure loss is probably given the most attention indepth in two studies [13] and [14]. In [13], the optimal geometrical parameters of the RHE are determined using the Pareto front concept; in [14] the boundaries of a more generalized porosity factor are defined for the typical operational conditions of the RHE.…”

“…Due to the aforementioned reasons, there are no distinct guidelines for designing an RHE, or they are too abstract. Although some sources [13], [14] and [18] suggest that the RHE with the highest temperature efficiency ratio would not be expected to be the most energy-efficient due to the high-pressure losses of such a heat exchanger. Therefore, this research focuses on the optimal ratio of temperature efficiency to pressure losses.…”

Robust Sliding Mode Control of Air Handling Unit for Energy Efficiency Enhancement

“…The cooling tower display is approved utilizing test information in a pilot plant. In [27], a point by point enhancement of plan parameters of warmth wheels is performed with a specific end goal to amplify sensible viability and to limit pressure drop. The investigation is brought out through a one-dimensional lumped parameters heat wheel model, which settles heat and mass exchange conditions, and through suitable relationships to appraise pressure drop.…”