The basis for a room global temperature

1992 ◽  
Vol 339 (1653) ◽  
pp. 153-191 ◽  
Keyword(s):  
Heat Transfer ◽  
Limited Extent ◽  
Point Temperature ◽  
Heat Flows ◽  
Heating And Cooling ◽  
Radiant Exchange ◽  
Least Squares Fit ◽  
Radiant Temperature ◽  
Building Heat ◽  
Bounding Surfaces

The design of heating and cooling appliances in buildings in routine cases normally proceeds on the assumption of a room index temperature which combines the separate effects of air temperature and of the longwave radiant field m the enclosure. It is pointed out that the basis for the index in current use in the U.K. and elsewhere is flawed, and this article is concerned with the logic of setting up a valid in ex temperature in its place. The argument depends first on reducing the surface-to-surface radiant exchange between enclosure surfaces to an approximately equivalent surface-to-star point exchange, using a least-squares fit. The fit proves to be quite good. It is next established that to a limited extent the star point temperature - a fictitious construct - will do duty for the space-averaged observable radiant temperature in the room. Thirdly, since the index temperature is taken to drive the radiant and convective heat flows from the room as a whole to one of its bounding surfaces, the question is discussed as to how reliably these physically dissimilar mechanisms can be formally merged in this way. Finally, simple expressions are given for enclosure heat needs in relation to comfort temperature and similar quantities. The arguments present some innovative features in building heat transfer.

Buildings

2017 ◽  
Author(s):  
Peter Rez
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Energy Efficient ◽  
Energy Use ◽  
Fossil Fuel ◽  
Local Climate ◽  
Heating And Cooling ◽  
The Difference ◽  
As If

Most of the energy used by buildings goes into heating and cooling. For small buildings, such as houses, heat transfer by conduction through the sides is as much as, if not greater than, the heat transfer from air exchanges with the outside. For large buildings, such as offices and factories, the greater volume-to-surface ratio means that air exchanges are more significant. Lights, people and equipment can make significant contributions. Since the energy used depends on the difference in temperature between the inside and the outside, local climate is the most important factor that determines energy use. If heating is required, it is usually more efficient to use a heat pump than to directly burn a fossil fuel. Using diffuse daylight is always more energy efficient than lighting up a room with artificial lights, although this will set a limit on the size of buildings.

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 Comparison of Building Simulation Methods for Modeling Apartment Balconies

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3955
Author(s):  
Yonghan Ahn ◽  
Hanbyeol Jang ◽  
Junghyon Mun
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Parameter Analysis ◽  
Interior Space ◽  
Heating And Cooling ◽  
Significant Difference ◽  
Calculation Results ◽  
Infiltration Parameter ◽  
The Difference ◽  
Heating And Cooling Load

The purpose of this study is to compare the load calculation results by a model using the air changes per hour (ACH) method and a model using an airflow network (AFN) and to ascertain what causes the difference between the two models. In the basic case study, the difference in the heat transfer distribution of the model in the interior space was investigated. The most significant difference between the two models is the heat transfer that results from infiltration. Parameter analysis was performed to investigate the relationship between the difference and the environmental variables. The result shows that the greater the difference is between the air temperature inside the balcony and the outdoor air temperature, and the greater the air flows from the balcony to the residential area, and the greater the heating and cooling load difference occurs. The analysis using the actual weather files of five domestic cities in South Korea rather than a virtual case shows that the differences are not so obvious when the wind blows at a constant speed throughout the year, but are dominant when the wind does not blow during the night and is stronger alongside the occurrence of sunlight during the day.

Modified methodology of computation of admissible continuous currents of plain conductors of overhead transmission lines and catenaries

2021 ◽  
Vol 2 (2) ◽  
pp. 36-43
Author(s):  
Evgeniy P. FIGURNOV ◽  
◽  
Yury I. ZHARKOV ◽  
Valeriy I. KHARCHEVNIKOV ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Transmission Lines ◽  
Power Transmission ◽  
Convection Heat Transfer ◽  
Heating And Cooling ◽  
Continuous Current ◽  
The Subject ◽  
The Common ◽  
Overhead Power Transmission Line

Methodology provided summarizes published, original and foreign theoretic and experimental data on the subject of heating and cooling of standard and shaped conductors of overhead power transmission line and uses those of them which are most affected to fundamental heat-transfer laws. Computation surface area of standard and shaped wire formulas are given. The common formula of convection heat transfer coefficient is provided, based on wind speed and direction, concerning antiicing mode. Parameters of this formula do not coincide with those existing, as they are based on experimental data on standard and shaped conductors but not on round tubes. Formula of computation of heat transfer power under the influence of solar radiation is given. Summarized formula of admissible continuous current computation is given, all the components have detailed description in the article.

scholarly journals Thermal behavior of premises equipped with different alveolar structures

2015 ◽  
Vol 19 (3) ◽  
pp. 929-938
Author(s):  
Nour Lajimi ◽  
Noureddine Boukadida
Keyword(s):  
Heat Transfer ◽  
Thermal Behavior ◽  
Air Temperature ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Point Temperature ◽  
Set Point ◽  
Alveolar Structure ◽  
Vertical Walls

This paper presents a numerical study of local thermal behavior. Vertical walls are equipped with alveolar structure and/or simple glazing in East, South and West frontages. Local temperature is assumed to be variable with time or imposed at set point temperature. Results principally show that the simple glazing number has a sensitive effect on convection heat transfer and interior air temperature. They also show that the diode effect is more sensitive in winter. The effect of alveolar structure and simple glazing on the power heating in case with set point temperature is also brought out.

scholarly journals Using buildings' foundation as a GHE in moderate climates

2020 ◽  
Author(s):  
Lazaros Aresti ◽  
Paul Christodoulides ◽  
Georgios A. Florides
Keyword(s):  
Heat Transfer ◽  
Reinforced Concrete ◽  
Heat Pumps ◽  
Scale Model ◽  
Space Heating ◽  
Zero Energy ◽  
Ground Source Heat Pumps ◽  
Heating And Cooling ◽  
Zero Energy Building ◽  
Energy Piles

<p>Shallow Geothermal Energy, a Renewable Energy Source, finds application through Ground Source Heat Pumps (GSHPs) for space heating/cooling via tubes directed into the ground. There are two main categories of Ground Heat Exchanger (GHE) types: the horizontal and the vertical types. Ground Heat Exchangers (GHEs) of various configurations, extract or reject heat into the ground. Even though GSHP have higher performance in comparison to the Air Source Heat Pumps (ASHPs), the systems high initial costs and long payback period have made it unattractive as an investment. GSHP systems can also be utilized in the buildings foundation in the form of Thermo-Active Structure (TAS) systems or Energy Geo-Structures (EGS), with applications such as energy piles, barrette piles, diaphragm walls, shallow foundations, retaining walls, embankments, and tunnel linings. Energy piles are reinforced concrete foundations with geothermal pipes, whereby the buildings foundations are utilized to provide space heating and cooling. Apart from energy piles, another EGS system can be achieved by the incorporation of the building’s foundation bed as a GHE. Foundation piles are not required in all constructions, but a building’s foundation bed is mandatory. This configuration is still based on the principles of the energy pile.</p><p>Energy piles have yet to be applied in Cyprus and, thus, a preliminary assessment considered and investigated before application would be useful. The potential of the GSHP systems by utilizing the building’s foundation through energy piles is considered here, for a moderate climate such as Cyprus, towards a Zero Energy Building. Typical foundation piles geometry in Cyprus consists of a 10m depth, a 0.4m diameter and reinforced concrete as a grout material, which is used at the foundation bed of the building. A typical dwelling in Cyprus is selected to be numerically modelled in this study. It is a three-bedroom, two-storey house with a 190m<sup>2</sup> total floor area, matching the thermal characteristics of a Zero Energy Building (i.e., U-values of 0.4W/m<sup>2</sup>/K on all walls and ceiling and 2.25 W/m<sup>2</sup>/K on all doors and windows, respectively). A full-scale model is developed in COMSOL Multiphysics software, to examine the energy rejected or absorbed into the ground by taking the heating and cooling loads of the typical dwelling in Cyprus. The convection-diffusion equation for heat transfer is used with the three-dimensional conservation of heat transfer for an incompressible fluid on all domains except the pipes, where a simplified equation is used. Different months in winter and summer are accounted for the simulations and the fluid-in – fluid-out temperature difference is presented. Finally, an economic evaluation of the systems examined above is presented, in order to check its viability. It is concluded that utilizing the dwelling’s foundations can be a better investment than using GHEs in boreholes.</p>

A two-port envelope model for building heat transfer

1998 ◽  
Vol 34 (1) ◽  
pp. 19-30 ◽  
Author(s):  
C. Lombard ◽  
E.H. Mathews
Keyword(s):  
Heat Transfer ◽  
Envelope Model ◽  
Building Heat
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