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Design for the Climate
Published in Dorothy Gerring, Renewable Energy Systems for Building Designers, 2023
Buildings are supposed to create comfortable conditions on the interior, no matter what the weather is outside. The psychrometric chart is used to identify temperature and relative humidity of air and is one of the tools used to size mechanical systems. Another tool is knowing the number of heating degree days (HDD) and cooling degree days (CDD) at a particular location. High numbers of HDD and/or CDD indicate a potential for needing a larger mechanical system, which will use energy to condition the air. Knowing the HDD and CDD, as well as other climate information, points the designer to what passive strategies could be appropriate for the building.
Psychrometrics
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Refrigeration is the process of cooling below ambient environmental temperature. Air conditioning (AC) is the process of treating air to simultaneously control its temperature, humidity, cleanliness, and distribution. Psychrometrics is the science of air/water vapor mixtures. It is used to study air at its various stages in the AC process and determine how the air moves from one state to another. The AC process changes the psychrometric condition of air and may involve cooling, heating, humidification, or dehumidification. This chapter provides a basic overview of psychrometrics as the underlying thermodynamic process involved in the application of certain technologies addressed in ensuing chapters in this Section. Examples include condensing methods, cooling towers, and desiccant dehumidification.
Psychrometric Performance Testing for HVAC&R Components and Equipment
Published in Josua P. Meyer, Michel De Paepe, The Art of Measuring in the Thermal Sciences, 2020
Orkan Kurtulus, Christian K. Bach, Romit Maulik, Omer San, Davide Ziviani, Craig R. Bradshaw, Eckhard A. Groll
Psychrometric rooms can provide various temperature and humidity conditions to simulate different climate zones and indoor environments to study the performance and behavior of the tested component or equipment. Testing HVAC&R components such as heat exchanger coils, air handling units, outdoor units, and heat pump water heaters requires temperature and humidity to be stable and within tight limits.
An instructional design for building energy simulation e-learning: an interdisciplinary approach
Published in Journal of Building Performance Simulation, 2019
Actually, in traditional multi-modular methods in mechanical engineering courses in Brazil, students learn in a progressive and not well interconnected way. (i) First, fundamentals of thermodynamics and transport phenomena are considered important prerequisites. (ii) Then, theoretical aspects on psychrometrics, HVAC (Heating, Ventilation and Air Conditioning) systems and solar geometry are taught. (iii) Next, energy and mass balances in buildings are physically and mathematically described, including parameters that are responsible for the building energy assessment. (iv) At that point, it is suitable to know the systems of equations to be solved, including the wall model (adding or not moisture related phenomena) and numerical method related parameters, to understand better, for instance, modelling limitations.
Model-based sensitivity analysis of barometric pressure on cooling capacity measurement of hydronic room fan coil units
Published in Science and Technology for the Built Environment, 2020
In addition to the impact on moist air density, the variation in barometric pressure indirectly affects the calculation of moist air enthalpy, humidity ratio, and specific heat. This impact is demonstrated in Figure 2, which shows the above three parameters calculated with a dry-bulb temperature of 26.7 °C (80.0 °F) and a wet-bulb temperature of 19.4 °C (67.0 °F) over a range of barometric pressure. The results were normalized against the corresponding values at the standard barometric pressure of 101.325 kPa (14.696 psia). As can be seen in Figure 2, psychrometric parameters have different sensitivities responding to barometric pressure changes. As the barometric pressure decreases from 105 kPa to 80.5 kPa (15 to 11.5 psia), the air specific heat increases less than 1% compared with the value at the standard barometric pressure. For the same barometric pressure change, however, the air enthalpy and humidity ratio increase by 14.1% and 36.1%, respectively. The large barometric pressure variation in Figure 2 could represent the variation induced by altitude changes. Figure 2 shows the barometric pressure dependency of using air dry- and wet-bulb temperatures to specify the air-side testing condition. Inconsistencies in FCU cooling capacity measurement could occur among testing locations with significant altitude changes. Considering that the weather-induced barometric pressure fluctuation in Figure 1 is less than the altitude-induced variation in Figure 2, the impact of barometric pressure on psychrometrics at a fixed location should be less severe than the results in Figure 2. However, a detailed analysis is still missing on how the weather-induced and altitude-induced barometric pressure variations influence the FCU cooling capacity measurement.