![]() In addition, we have confirmed that COP (1) during the chilled water production operation may be improved by about 10% if an open motor is mounted on the heat pump units. This serves to stabilize the refrigerant pressure. The difference between COP (1) and COP (2) is small compared to similar machines because the fan drive power for the air/refrigerant heat exchanger was reduced for sound attenuation and because the unit is automatically started and stopped following fluctuations in the outdoor air temperature. These values will improve in the future as the amount of energy produced increases. Furthermore, the average COP (1) for August is 3.06 and the average COP (2) is 2.85. This data shows that the average COP (1) for February is 2.70 and the average COP (2) is 2.44. COP (2) is evaluated using an input which includes the air/refrigerant heat exchanger fan and the primary pump drive power in addition to the compressor input. It is seen that the performance values obtained here are similar.ĬOP (1) is evaluated using the amount of chilled water and hot water produced as the output with the energy required to drive the compressor as the lone input. , which used a vertical heat exchanger at a depth of 80 m, reported a COP sys of 4.4–4.5. In addition, the summer research of Michopoulos et al. revealed a COP for GCHP systems of 4.19–4.57 in the winter season and 3.9–4.53 in the summer season. The COP values of the GCHP system were compared to the existing COP values applied in GCHP research. This is because the heating load was higher than the cooling load, and in addition, the electricity consumption in heating operation was higher than the electricity consumption in cooling operation. The comparison of the GCHP system experimental performances in the heating and cooling operation ( Tables 7.1 and 7.2) indicate that the system performance in heating and cooling operation was almost equal. ![]() Long-wave radiationĪ fictive sky temperature, dependent on ambient temperature, emissivity, and cloudiness, is introduced to account for the long-wave radiative heat exchange between the building envelope and the sky. Normally, thermal building-dynamics simulation programs allow for the consideration of such shading. Also, certain wings or parts of the building itself may shade the part under investigation permanently or over certain time periods. Since insolation often has a very significant effect on the heat balance of a building, shading by buildings or other objects in the surroundings of the building must be taken into account. Normally, for energy analysis, this is not critical, but it may have a significant effect on the natural ventilation of multistory buildings. ![]() Neither effect normally is accounted for in building simulation programs. This changes the convective heat transfer and leads to increased temperatures of supply air for natural ventilation. In low-wind conditions, free convective flows drift up the warm external wall surface. The solar radiation absorbed on external building surfaces increases the wall surface temperature, thus leading to a change in the heat conducted through the component. Depending on the model used, discrepancies for the boundary conditions may occur with the same basic set of solar radiation data, thus leading to differences in the simulation results. Several diffuse sky models are available. It is composed of three parts, referred to as isotropic, circumsolar, and horizontal brightening. The diffuse sky radiation is not uniform. For nonhorizontal surfaces, the diffuse radiation is composed of the contribution from the diffuse sky and reflections from the ground. In the simulation, solar radiation input values must be converted to radiation values for each surface of the building. The total or global solar radiation has a direct part (beam radiation) and a diffuse part (see Fig. Wind affects the convective heat transfer on external walls and is a driving force for natural ventilation. Year-round outdoor air humidity must be considered when studying condensation conditions. Outdoor air humidity strongly affects the latent cooling load and energy requirements during the summer season. Moreover, outdoor air temperature is a driving force for natural ventilation, as the difference between indoor and outdoor air temperature causes the stack effect. Outdoor air temperature affects the heat transfer through external walls and roofs and the heat transfer by ventilation. Outdoor air temperature is an important factor regarding the building energy balance. Yang Yang, in Industrial Ventilation Design Guidebook (Second Edition), 2021 3.4.2.4 Outdoor conditions Outdoor air temperature
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