Abstract:In the present study, we have developed an optimal heat supply algorithm which minimizes the heat loss through the distribution pipe line in a group energy apartment. Heating load variation of a group energy apartment building according to the outdoor air temperature was predicted by a correlation obtained from calorimetry measurements of all households in the apartment building. Supply water temperature and mass flow rate were simultaneously controlled to minimize the heat loss rate through the distribution pipe line. A group heating apartment building located in Hwaseong city, Korea, which has 1473 households, was selected as the object building to test the present heat supply algorithm. Compared to the original heat supply system, the present system adopting the proposed control algorithm reduced the heat loss rate by 10.4%.

Abstract:In the present study, a fuel cell driven ground source heat pump (GSHP) system is applied in a community building and heat pump system performance is analyzed by computational methods. Conduction heat transfer between the brine pipe and ground is analyzed by TEACH code in order to predict the performance of the heat pump system. The predicted coefficient of performance (COP) of the heat pump system and the energy cost were compared with the variation of the location of the objective building, the water saturation rate of the soil, and the driven powers of the heat pump system. Compared to the late-night electricity driven system, a significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system. This is due to the low cost of electricity production of the fuel cell system and to the application of the recovered waste heat generated during the electricity production process to the heating of the community building.

To examine the characteristics of turbulent flow and heat transfer about the compound channel with gap, the present study has performed a numerical analysis by using large eddy simulation (LES). Our first aim was to analyze the cause of pulsating flow by investigating the turbulent flow through the unsteady analysis of compound channel. Next, to understand the correlations between gap width and heat transfer enhancement, we tried to verify the enhancement effect of heat transfer when a gap exists within the compound channel. From this numerical analysis, we could see that the lateral velocity occurs periodically around the gap and this is developed in the pulsating flow. The pulsating flow has generated a strong turbulent flow mixing within the compound channel. And the turbulent flow mixing in the pulsating flow plays an effective role of enhancing heat transfer effect by making the fluid temperature uniformly within the compound channel.

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The purpose of this study is to theoretically supplement the dissipation rate equation model that has been adopted and used for the elliptic-blending second-moment closure widely and currently used for analysis of turbulent flow, and eventually to enhance the theoretical validity of the model. The new dissipation rate equation model was derived by using the dissipation rate equation in terms of length scale that can be applied both in the near-wall region and to homogeneous flow and by using the dissipation rate tensor equation model. The newly derived dissipation rate equation model is applied in the existing elliptic-blending model as it is. To test the model equation we conducted a numerical analysis of non-rotating and rotating channel flows, channel flow with uniform transpiration, square duct flow, and 3-dimensional curved duct flow before comparing the analysis results with DNS data and the measurements. In regard to all flow fields adopted in this study, the expected results showed a high satisfaction in comparison with DNS data and measurements, thereby proving the theoretical validity of the new model.