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Unitary HVAC Systems
Published in Vishal Garg, Jyotirmay Mathur, Surekha Tetali, Aviruch Bhatia, Building Energy Simulation, 2017
Vishal Garg, Jyotirmay Mathur, Surekha Tetali, Aviruch Bhatia
In most unitary HVAC systems, coefficient of performance (COP) and fan properties are the two key aspects that govern their energy consumption. Higher COP is associated with a reduction in energy consumption. Unitary systems require a fan for blowing air over the condenser as well as evaporator tubes. A fan is characterized by its static pressure and volumetric air flow rate. High static pressure and flow rate help in achieving setpoint faster, however, they are also associated with higher energy consumption. If these parameters are not specified properly, results of the energy model could significantly deviate from the actual performance. This chapter explains the method of modelling unitary systems by specifying COP and fan properties.
Primary Heating and Cooling Systems
Published in Moncef Krarti, Energy Audit of Building Systems, 2020
Generally, the energy efficiency of a cooling system is characterized by its coefficient of performance (COP). COP is defined as the ratio of the heat extracted divided by the energy input required. In the case of an electrically driven cooling system as represented in Figure 8.6, COP can be expressed as: COP=QcoolWcomp
HVAC Systems Concepts
Published in Herbert W. Stanford, Adam F. Spach, Analysis and Design of Heating, Ventilating, and Air-Conditioning Systems, 2019
Herbert W. Stanford, Adam F. Spach
ASHRAE Standard 90.1 defines efficiency on the basis of specific required minimum performance measurements: For cooling by units rated with a cooling output of less than 65,000 Btu/h [19 kW], seasonal energy efficiency ratio (SEER) is defined as the total cooling output of the heat pump during its normal cooling usage period (in Btu) divided by the total electric energy input during that same period (in Watt-hours).For cooling by units rated with a cooling output of 65,000 Btu/h [19 kW] or greater, energy efficiency ratio (EER) is defined as the ratio of net cooling capacity (in Btu/h) to the total rate of electrical input (in watts) under designated operating conditions.For heating by units rated with a cooling output of less than 65,000 Btu/h [19 kW], heating seasonal performance factor (HSPF) is defined as the total heating output of the heat pump during its normal heating usage period (in Btu) divided by the total electric energy input during that same period (in Watt-hours).For heating by units rated with a cooling output of 65,000 Btu/h [19 kW] or greater, heating efficiency is defined in terms of coefficient of performance (COP). COP is a dimensionless value defined as the net heating capacity of the heat pump (in Btu/h [kW]) divided by the energy input (in Btu/h [kW]) under designated operating conditions.
The impact of extreme weather on peak electricity demand from homes heated by air source heat pumps
Published in Energy Sources, Part B: Economics, Planning, and Policy, 2021
Michael Chesser, Padraic O'Reilly, Padraig Lyons, Paula Carroll
HPs are promoted as an attractive renewable alternative for residential consumers to replace fossil fuel heating systems. They are advertised as low maintenance systems offering lower costs, contributing to lowering carbon emissions and improving local air quality. HPs are energy recovery systems that use electricity to extract heat from an external source and transform it for use in the building’s heating system. Additional benefits accrue when the electricity used to operate the HPs comes from renewable energy systems (Carroll, Chesser, and Lyons 2020). A schematic of the HP process can be seen in Figure 1. It shows an HP, in this case an ASHP, powered by electricity from the gird to extract heat from the outside air. This heat energy is absorbed by the coolant liquid in the evaporator (blue). The coolant is compressed to a higher pressure increasing its temperature. The coolant than condenses in the water cooled condenser (red), transferring heat to the house’s heating system. The coefficient of performance (COP) metric is used to gauge how efficiently a HP does this. The COP is defined as the ratio of heating provided by the HP to the electricity consumed by the HP.
Elimination of multidimensional outliers for a compression chiller using a support vector data description
Published in Science and Technology for the Built Environment, 2021
To investigate the scalability performance of both the ANNraw and the ANNSVDD models, the correlations between Tbrine, inlet and the chiller’s COP and between Tcool, inlet and the chiller’s COP were analyzed. The data acquired with chiller powers in the range from 195 kW to 205 kW were used to analyze the correlations because the mode of the measured chiller power was approximately 200 kW. As shown by the dashed red lines (Figure 10), the chiller’s COP exhibits a positive correlation with the brine inlet temperature. As the brine inlet temperature increases, the COP increases. In addition, the chiller’s COP exhibits a negative correlation with the cooling water inlet temperature. As the cooling water inlet temperature decreases, the COP increases.
High performance electrostatically driven thermal switch incorporated with a mini-channel cooling
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Jiuming Ma, Xiaotong Lin, Mingjian Xian, Xiufang Ke, Dongliang Lu, Yingbang Yao, Tao Tao, Bo Liang, Sheng-Guo Lu
Active devices need to consume extra energy in order to serve their purpose. COP is an important parameter to evaluate the energy transferred efficiency of active devices. The higher the COP, the higher energy utility efficiency and then, the more economical of the devices. In order to achieve a better cooling effect, much energy needs to be input into the system, and, as a result, the COP will decrease. The relationship between COP and CHTC is shown in Figure S3 of the Supplementary Material. When the average CHTC was 6,839 mW/cm2·K, the COP value of the proposed thermal switch was is the transferred heat and is the total input energy which is the sum of voltage source power (0.5 mW) and pump power (0.2～9.5 W), which was more than double that of conventional evaporative cooling devices.