Improved Thermal Comfort of Office Occupants Through Better Air Diffuser Designs

2015 ◽  
Author(s):  
Yu-Cheng Liu ◽  
Mihai G. Burzo ◽  
Scott Sier ◽  
Cassandra Ellis
Keyword(s):  
Thermal Comfort ◽  
Cfd Analysis ◽  
Hvac System ◽  
Vertical Temperature ◽  
Cooling Mode ◽  
Air Jets ◽  
Heating And Cooling ◽  
Air Diffusion ◽  
Heating Mode ◽  
Vane Diffuser

In this work we are exploring the influence of the design of air diffusers on a number of parameters that influence the thermal comfort of building occupants. In particular we are looking at calculating the Air Diffusion Performance Index (ADPI) and vertical temperature difference as well as the throw and drop parameters for various diffuser designs. The results show that while a complex radial vane diffuser that uses the Coanda effect could offer good performance if the HVAC system is used for cooling, the same design might not give any advantage as compared to a regular multi-cone design while the system is used for heating. This is mostly due to the strong air stratification observed for both diffuser designs, while the HVAC system is in the heating mode. Consequently we propose a better alternative, namely, to use a variable geometry (angle) air diffuser. To prove this concept we performed a CFD analysis of several diffusers, each delivering the air at different angles, for both heating and cooling mode, and we show that indeed using a design that allows changing the angle of the air jets between the heating and cooling season is the optimal way of delivering air to a room.

scholarly journals Numerical Study on Effects of Air Return Height on Performance of an Underfloor Air Distribution System for Heating and Cooling

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1070
Author(s):  
Yaming Fan ◽  
Xiangdong Li ◽  
Minfeng Zheng ◽  
Rengui Weng ◽  
Jiyuan Tu
Keyword(s):  
Energy Consumption ◽  
Air Quality ◽  
Thermal Comfort ◽  
Distribution System ◽  
Numerical Study ◽  
Air Distribution ◽  
Cooling Mode ◽  
Design And Optimization ◽  
Heating And Cooling ◽  
Heating Mode

The exhaust/return-split configuration is regarded as an important upgrade of traditional under-floor-air-distribution (UFAD) systems due to its higher energy efficiency. Moreover, existing studies are mostly focused on the effect of the return vent height on the performance of an UFAD system under cooling conditions. Knowledge of the performance under heating conditions is sorely lacking. This paper presents a numerical evaluation of the performance characteristics of an UFAD system with six different heights of the return vents in heating operation by comprehensively considering thermal comfort, air quality, and energy consumption. The results show that, in the heating mode, the general thermal comfort (predicted mean vote-predicted percentage dissatisfied (PMV-PPD) values) and indoor air quality indices (mean age of air and volatile organic compounds (VOCs) concentration) were greatly improved and energy consumption was slightly reduced with a lower return vent height. Although these were opposite to the findings of our previous study regarding the performance in cooling mode, an optimal return vent height in terms of the comprehensive all-year performance can be recommended. This method provides insight into the design and optimization of the return vent height of UFAD for space heating and cooling.

Thermal Performance of a Combined Heat, Cooling, and Power Microturbine System

2009 ◽  
Author(s):  
Hannu E. Ja¨a¨skela¨inen ◽  
James S. Wallace
Keyword(s):  
Waste Heat ◽  
Lithium Bromide ◽  
Hot Water ◽  
Cooling Mode ◽  
University Of Toronto ◽  
Heating And Cooling ◽  
Thermal Output ◽  
Operating Constraints ◽  
The University ◽  
Heating Mode

A 240 kWe integrated microturbine chiller/heater system was installed on the campus of the University of Toronto at Mississauga in 2005 to provide heating or cooling in combination with electric power generation. The system consists of four 60 kWe microturbines fueled by natural gas and a 110 ton lithium bromide absorption chiller that utilizes waste heat from the microturbines. The chiller can be operated in cooling mode to supply chilled water in summer for cooling or in heating mode to supply hot water (60°C) in winter for heating. Tests were conducted in both heating and cooling mode to evaluate the effectiveness of heat recovery and results are presented for both modes of operation. However, operating constraints imposed by this particular installation prevent full utilization of thermal output in both heating and cooling mode. Recommendations are provided to guide future installations to make full use of the equipment’s potential.

scholarly journals Geothermal energy: shallow sources

2014 ◽  
Vol 126 (2) ◽  
pp. 25
Author(s):  
Ian Johnston
Keyword(s):  
Heat Pump ◽  
Geothermal Energy ◽  
Heat Pumps ◽  
Cooling Mode ◽  
Ground Source Heat Pumps ◽  
Heating And Cooling ◽  
Ground Source ◽  
Heating Mode ◽  
To Receive ◽  
Ground Energy

Below a depth of around 5 to 8 metres below the surface, the ground displays a temperature which is effectively constant and a degree or two above the weighted mean annual air temperature at that particular location. In Melbourne, the ground temperature at this depth is around 18°C with temperatures at shallower depths varying according the season. Further north, these constant temperatures increase a little; while for more southern latitudes, the temperatures are a few degrees cooler. Shallow source geothermal energy (also referred to as direct geothermal energy, ground energy using ground source heat pumps and geoexchange) uses the ground and its temperatures to depths of a few tens of metres as a heat source in winter and a heat sink in summer for heating and cooling buildings. Fluid (usually water) is circulated through a ground heat exchanger (or GHE, which comprises pipes built into building foundations, or in specifically drilled boreholes or trenches), and back to the surface. In heating mode, heat contained in the circulating fluid is extracted by a ground source heat pump (GSHP) and used to heat the building. The cooled fluid is reinjected into the ground loops to heat up again to complete the cycle. In cooling mode, the system is reversed with heat taken out of the building transferred to the fluid which is injected underground to dump the extra heat to the ground. The cooled fluid then returns to the heat pump to receive more heat from the building.

Achievement of Geothermal Energy Using Ground Heat Exchanger in Ma'En

2011 ◽  
Vol 22 (8) ◽  
pp. 1029-1050 ◽  
Author(s):  
Mohammed Awwad Ali Al-Dabbas
Keyword(s):  
Heat Exchanger ◽  
Geothermal Energy ◽  
Design Procedure ◽  
Ground Heat Exchanger ◽  
Cooling Mode ◽  
Geothermal Fluid ◽  
Heating And Cooling ◽  
Low Emission ◽  
Fluent Software ◽  
Heating Mode

Geothermal energy in Jordan is a low-emission and renewable source that could provide households and commercial buildings with both heating and cooling. Access to this ‘free’ energy may be available just a few feet underground. Thus, the objectives of this research are: Designing ground heat exchanger to utilize geothermal energy in heating in which the primary geothermal fluid is exchanged with secondary clean fluid The feasibility of designing ground heat exchanger system to pumping geothermal energy under the climate of Jordan weather in Ma'en area Amount of energy saved The design procedure involves applying the energy and the momentum equations around the geothermal fluid circuit. The FLUENT software program is used to calculate the ground heat exchanger parameters and the amount of energy saved. Finally, the feasibility study shows that the Geoexchange systems represent a savings to homeowners of around 70% in the heating mode, and up to 50% in the cooling mode compared with conventional fossil fuel systems.

Absorption Heat Pump Performance Improvement Through Ground Coupling

1997 ◽  
Vol 119 (4) ◽  
pp. 242-249 ◽  
Author(s):  
S. Garimella
Keyword(s):  
Heat Pump ◽  
Coupled System ◽  
Climate Data ◽  
Ambient Conditions ◽  
Cooling Mode ◽  
Heat And Mass Exchange ◽  
Absorption Heat Pump ◽  
Heating And Cooling ◽  
Residential Space ◽  
Heating Mode

The present study investigates the improvement in the performance of an absorption heat pump for residential space-conditioning due to the use of the ground as the heat source in the heating mode and the heat sink in the cooling mode. A baseline air-coupled single-effect ammonia-water heat pump is first designed to deliver 10.55 kW (36,000 Btu/h) of cooling load at the ARI rating conditions. Particular attention is paid to incorporating many realistic details of an operating system such as fuel combustion efficiencies of the burner, nonequilibrium conditions, and moist air processes in the air-coupled heat exchangers. A range of parametric studies is also conducted to investigate the variation in performance of this system with ambient conditions in the heating and cooling modes. The same system is then analyzed in a ground-coupled configuration. The instantaneous COP for the ground-coupled system is compared with the COP of the air-coupled system as a function of the time of the year and the corresponding variations in ambient and ground temperatures using 30-yr average climate data for various locations from the National Weather Service. Improvements in COP of up to 20 percent over the air-coupled system values (cooling mode COP of 0.495 at 35°C (95°F) and heating mode COP of 1.20 at 8.33°C (47°F)) are demonstrated in diverse geographic locations with widely varying heating and cooling loads. These improvements indicate that an efficient ground-coupled heat pump could be developed for residential space-conditioning applications using simple thermodynamic cycles and existing technology for the heat and mass exchange components.

scholarly journals Experimental Study of a Gas Engine-driven Heat Pump System for Space Heating and Cooling

2019 ◽  
Vol 5 (10) ◽  
pp. 2282-2295 ◽  
Author(s):  
Wei Zhang ◽  
Xianzhao Yang ◽  
Tao Wang ◽  
Xueyuan Peng ◽  
Xiaolin Wang
Keyword(s):  
Flow Rate ◽  
System Performance ◽  
Energy Input ◽  
Water Flow Rate ◽  
Cooling Capacity ◽  
Space Heating ◽  
Cooling Mode ◽  
Gas Engine ◽  
Heating And Cooling ◽  
Heating Mode

In this paper, the performance of a gas engine-driven heat pump (GEHP) was experimentally studied for space heating and cooling. An experimental test facility was developed for this purpose. The effect of key parameters on system performance was investigated under both cooling and heating modes. The results showed that as the engine speed increased from 1400 to 2000 rpm, the cooling and heating capacities increased by 23% and 28.5%, respectively while the GEHP system Primary Energy Ratio (PER) decreased by 13.5% and 11.7% in the cooling and heating modes, respectively. The system PER in the cooling mode was found lower than that in the heating mode. This indicated that heat recovery from the engine cylinder and exhaust gas was very important for improving the GEHP system performance. In the heating mode, the ambient temperature and condenser water flow rate had a large effect on the system heating capacity and PER, and insignificant effect on the gas energy input. In the cooling mode, the chilled water inlet temperature showed a large effect on both cooling capacity and gas energy input while the chilled water flow rate had a large effect on cooling capacity and insignificant effect on the gas energy input.

scholarly journals Experimental study of the performance of a vertical and a horizontal ground loops coupled to a ground source heat pump system

2021 ◽  
Author(s):  
Waleed S. Alzahrani
Keyword(s):  
Heat Pump ◽  
Ground Source Heat Pump ◽  
Cooling Mode ◽  
Pump System ◽  
Heat Pump System ◽  
Heating And Cooling ◽  
Ground Source ◽  
Vertical Ground ◽  
Set Up ◽  
Heating Mode

The performance of vertical and horizontal ground loops coupled to a Ground-Source Heat Pump (GSHP) was investigated under four different scenarios. For this purpose, an experimental set-up was designed and constructed at the Archetype Sustainable houses in Vaughan, Ontario, Canada. In the first two tests, the two vertical ground loops coupled to the GSHP were tested in heating, and cooling modes. In heating mode, the GSHP COP ranged between 2.7 and 3.15. In cooling mode, the GSHP performed better than the heating mode with COP range of 3.75 and 5.4. In the last two tests, two scenarios were tested to compare the horizontal and the vertical ground loops in cooling mode. In the first scenario, the ground loop flow was divided equally between the loops and the GSHP overall COP was 5.42. The last test used equal Reynolds number in both loops and the GSHP overall COP was 5.36.

scholarly journals Experimental study of the performance of a vertical and a horizontal ground loops coupled to a ground source heat pump system

2021 ◽  
Author(s):  
Waleed S. Alzahrani
Keyword(s):  
Heat Pump ◽  
Ground Source Heat Pump ◽  
Cooling Mode ◽  
Pump System ◽  
Heat Pump System ◽  
Heating And Cooling ◽  
Ground Source ◽  
Vertical Ground ◽  
Set Up ◽  
Heating Mode

The performance of vertical and horizontal ground loops coupled to a Ground-Source Heat Pump (GSHP) was investigated under four different scenarios. For this purpose, an experimental set-up was designed and constructed at the Archetype Sustainable houses in Vaughan, Ontario, Canada. In the first two tests, the two vertical ground loops coupled to the GSHP were tested in heating, and cooling modes. In heating mode, the GSHP COP ranged between 2.7 and 3.15. In cooling mode, the GSHP performed better than the heating mode with COP range of 3.75 and 5.4. In the last two tests, two scenarios were tested to compare the horizontal and the vertical ground loops in cooling mode. In the first scenario, the ground loop flow was divided equally between the loops and the GSHP overall COP was 5.42. The last test used equal Reynolds number in both loops and the GSHP overall COP was 5.36.

scholarly journals Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3298
Author(s):  
Gianpiero Colangelo ◽  
Brenda Raho ◽  
Marco Milanese ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Cooling System ◽  
Electrical Energy ◽  
Simulation Software ◽  
Heat Transfer Fluid ◽  
Hvac System ◽  
Dynamic Simulations ◽  
Heating And Cooling ◽  
The University

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.

scholarly journals Heating and Cooling Degree-Days Climate Change Projections for Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 715
Author(s):  
Cristina Andrade ◽  
Sandra Mourato ◽  
João Ramos
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Thermal Comfort ◽  
Energy Demand ◽  
Residential Buildings ◽  
Degree Days ◽  
Climate Change Projections ◽  
Heating And Cooling ◽  
Cooling Degree Days ◽  
Heating Energy Demand

Climate change is expected to influence cooling and heating energy demand of residential buildings and affect overall thermal comfort. Towards this end, the heating (HDD) and cooling (CDD) degree-days along with HDD + CDD were computed from an ensemble of seven high-resolution bias-corrected simulations attained from EURO-CORDEX under two Representative Concentration Pathways (RCP4.5 and RCP8.5). These three indicators were analyzed for 1971–2000 (from E-OBS) and 2011–2040, and 2041–2070, under both RCPs. Results predict a decrease in HDDs most significant under RCP8.5. Conversely, it is projected an increase of CDD values for both scenarios. The decrease in HDDs is projected to be higher than the increase in CDDs hinting to an increase in the energy demand to cool internal environments in Portugal. Statistically significant linear CDD trends were only found for 2041–2070 under RCP4.5. Towards 2070, higher(lower) CDD (HDD and HDD + CDD) anomaly amplitudes are depicted, mainly under RCP8.5. Within the five NUTS II

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