Heat and ventilation

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Plate heat exchanger design: a case study for ventilation systems of small residences

Plate heat exchanger design: a case study for ventilation systems of small residences

In air-to-air PHEs used in ventilation systems, fresh air and stale air streams are separated by a plate. As the temperature difference between the two air streams continues, the heat energy in the hot air stream is transferred to the cold air stream through the plate between the fresh air and stale air stream, according to the first law of thermodynamics. Thus, the heat in the hot and stale indoor air, which must be removed from the building, is transferred to the cold and fresh outdoor air which must be taken into the building. Heat transfer may also be in the opposite direction in term of seasonal conditions. A very cold or very hot air flow, while blown through a heat recovery ventilation system, discomfort to the people indoor. In other words, the temperature of the air supplied from the heat exchanger is desirable close to the indoor air conditions. On the other hand, a heat exchanger's supply of air at the right temperature does not mean that it works effectively. If sufficient heat recovery is not ensured, sufficient savings cannot be made economically [1, 4].

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Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

There was much effort to investigate the complex cooling system of turbine generator. Yoo et al., [1] reported the detail heat transfer and pressure loss characteristics of rotor ventilation duct applying experimental and CFD approaches. In the air gap, the spent cooling air from rotor and stator meets and interacts with rotating and stationary geometries. Han et al., [2], Tang et al., [3] and Mayle et al., [4] investigated flow characteristics and thermal characteristics in the air gap for an air- cooled turbine generator using numerical and experimental methods. The end winding has complicated configuration connecting the stator bars in multiple locations. Tong [5] and Ujiie et al., [6] studied the flow field and heat transfer coefficient near end-winding using numerical method. Klomber et al., [7] propose correlations between the convective wall heat transfer coefficient and speed and flow rate parameters near end-winding region. Furthermore, the flow field near end- winding of hydrogenator for various ventilation scheme is reported [8]. The studies on the flow field of stator cooling system of hydrogenator was carried out by Carew and Freeston [9], and Schirittweiser [10]. They show that major parts of the total pressure losses occur near wedge region. Shuye [11], Guanbushanam et al., [12] and Pasha et al., [13] investigated hydraulic loss factor and overall pressure drop of stator ventilation ducts. There are also reports [14,15] on the detail pressure distribution on the stator ventilation ducts of hydrogenator, especially in the vicinity of stator bar. Li et. al., [16] investigated flow rate distribution of stator ventilation ducts by varying axial velocity at the entrance of air gap.

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Numerical and experimental analysis of a natural ventilation windcatcher with passive heat recovery for mild-cold climates

Numerical and experimental analysis of a natural ventilation windcatcher with passive heat recovery for mild-cold climates

In this study, the air flow through a windcatcher with a rotary heat recovery wheel was investigated using CFD modelling. It has been shown in previous work that windcatchers are capable of delivering the guideline levels of ventilation into a room, therefore the rotary wheel should not reduce the air supply rate to unsuitable levels to provide adequate ventilation to be an effective system. The numerical modelling was validated against experimental models tested in a closed-loop wind tunnel. The comparison between the CFD and experimental model showed a good correlation between the two sets of data. Results showed that the addition of heat recovery had a positive effect on the indoor air temperature, raising the temperature between 1-4 K depending on the outdoor wind conditions. According to WBCSD [2], a recovery of 3 K from the exhaust stream to the inlet stream could generate energy savings up to 20% in heating costs. This shows that the concept has significant potential to be developed further, whereby the heat transfer properties of the system can be investigated and tested on a larger scale.

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Analysis of a rotary passive heat recovery device for natural ventilation windcatcher

Analysis of a rotary passive heat recovery device for natural ventilation windcatcher

Four regulated similar axial fans were incorporated at every channel to drive the air flow. Air is drawn from the duct inlets through the channel by the axial fans (suction driven flow). This arrangement showed the greatest uniform velocity profile in the channels. Many of the elements such as casing and rotary wheel were nonstandard and needed the use of 3D printing. Figure 4 demonstrates the total dimension of the ductwork with 5 mm acrylic Perspex material. Casing of the heat recovery system sit flush in the ductwork and any air gaps were closed at the time of experimental testing such as measurement points that are unused. The copper plates were applied for the heat recovery radial blades having 100 mm x 100 mm x 1mm dimensions. The rotary wheel’s inner shell with diameter 0.145 m was built to house the radial blades. For the system to rotate, a toothed gear incorporated to a small motor was used. While for the outer shell, it was built to match the teeth on the gear to let the wheel rotate smoothly. In order to build the shell accurately, 3D printing was utilized. To examine the response of the passive rotary wheel on the supply air ventilation level, air flow velocity measurements were conducted. As mentioned in the previous section, low pressure drop over the system was required to make sure that the needed ventilation levels will be reached even at low wind speeds. Velocity measurements were conducted through utilising Testo 425 hot wire anemometer with resolution of 0.01m/s and an accuracy of 0.03 m/s +5%rdg. In every calculation area, the air velocity was calculated for twenty seconds and the mean velocity rate was recorded. The measurement was conducted three times for every area. Air temperature was taken at similar areas with the use of Testo 176 P1 logger, resolution of 0.1°C, and accuracy of 0.03°C. Simultaneous measurements were used for the entire data collection points, every five seconds for one hour. Monitoring was carried out in a long period of time with slow alterations in the air flow setting.

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DEVELOPMENT OF CONSTRUCTION OF A CATALYTIC REACTOR FOR METHANE OXIDISING IN VENTILATION AIR IN COAL MINES AND THE RESEARCH ON INTEGRATED “HEAT PIPE” RECUPERATOR

DEVELOPMENT OF CONSTRUCTION OF A CATALYTIC REACTOR FOR METHANE OXIDISING IN VENTILATION AIR IN COAL MINES AND THE RESEARCH ON INTEGRATED “HEAT PIPE” RECUPERATOR

tem require further research and development of the issue [5]. The works were undertaken by the Consortium of Methane Utilisation from Coal Seams, established by AGH University of sci- ence and Technology, Wrocław University of Technology and Maria Curie-Skłodowska Uni- versity. One of the consortium tasks was to con- struct an experimental large-size installation for catalytic oxidation of methane from ventilation air in coal mines and the tests on both the cata- lysts and the whole installation. The key issue for the quality of the planned research tasks, aimed at magnifying the scale, was to select the type and form of catalytic reactor construction and heat exchanger.

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VENTILATION SYSTEM WITH GROUND HEAT EXCHANGER

VENTILATION SYSTEM WITH GROUND HEAT EXCHANGER

The modern standard of living makes a man demands increasing amount of indoor air quality. Conditions in which a person feels comfortable greatly affects not only his well-being, but also job performance, which translates into operat- ing costs of the system. People spend large part their lives in closed spaces. This applies to both apartments, as well as rooms for work. Currently, in the newly constructed production facilities, of warehouse, office and public buildings air-con- ditioning and ventilation systems is a standard building equipment. Using air conditioning sig- nificantly improves conditions in the room, but it requires huge amounts of energy supply in or- der to function properly. Costs of production of thermal energy to heat the outside air to the value required for correct operation of air-conditioning systems may already be a heavy burden for the investor. However, these costs can be lowered by heat recovery systems from the exhaust air from the room. The paper has taken under consider- ation the systems based on alternative heat sourc- es as ground. This renewable energy source are is

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A study of passive ventilation integrated with heat recovery

A study of passive ventilation integrated with heat recovery

To meet the demand for energy demand reduction in heating, ventilation and air-conditioning systems, a novel design incorporating a heat recovery device into a wind tower was proposed. The integrated system uses a rotary thermal wheel for heat recovery at the base of the wind tower. A 1:10 scale prototype of the system was created and tested experimentally in a closed-loop subsonic wind tunnel to validate the Computational Fluid Dynamics (CFD) investigation. Wind towers have been shown to be capable of providing adequate ventilation in line with British Standards and the Chartered Institution of Building Services Engineers (CIBSE) guidelines. Despite the blockage of the rotary thermal wheel, ventilation rates were above recommendations. In a classroom with an occupancy density of 1.8m 2 /person, the wind tower with rotary thermal wheel was experimentally shown to provide 9L/s per person at an inlet air velocity of 3m/s, 1L/s per person higher than recommended ventilation rates. This is possible with a pressure drop across the heat exchanger of 4.33Pa. In addition to sufficient ventilation, the heat in the exhaust airstreams was captured and transferred to the incoming airstream, raising the temperature 2°C, this passive recovery has the potential to reduce demand on space heating systems.

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Modeling of Grain Storage Ventilation Based on BP Neural Network

Modeling of Grain Storage Ventilation Based on BP Neural Network

In one aeration system, the initial grain moisture content, the inlet air temperature and relative humidity, and the aeration duration would all influence the stored grain ventilation process. The first three parameters were usually known, but the ventilation duration needed to be calculated. Therefore, the heat transfer and mass transfer theoretical model was used to calculate the ventilation duration first under different inlet air conditions [3]. Then the model was used to simulate the grain temperature, humidity and grain under different initial moisture, under different initial grain moisture content, inlet air temperature, relative humidity of the inlet air and ventilation duration.

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Piglets Comfort with Hot Water by Biogas Combustion under Controllable Ventilation

Piglets Comfort with Hot Water by Biogas Combustion under Controllable Ventilation

The stoking density of piglets in the enclosed pigsty is 1.77 pig/ m 2 , under the setting of 28° C for both defaulted air temperature and forced ventilation te mperature in the pigsty, collocate with different a ir change rate of regular ventilation, i.e. 1.7 A CH, 3.4 ACH and 5.1 A CH to perfo rm the e xperiment. The concentration of ca rbon dio xide at diffe rent air change rate of regular ventilation are lower than 900 pp m, it is able to stably ma intain the temperature, re lative humidity and concentration of carbon dioxide in the nursery, and achieve the effective heat preservation effect, and maintain the good air quality in the pigsty. When the air change rate of regular ventilation is configured as 5.1 ACH, the concentration of carbon dio xide in the pigsty is quite close to the 400 pp m concentration of carbon dioxide outside the nursery, it is indicated that the air quality in the pigsty is very good. As known fro m the e xpe rimental results, this biogas burn ing hot-water system co llocating with inverter fan to perfo rm the ventilation in enclosed the pigsty, the temperature change in the pigsty is quite un iform, apply to the heat preservation for the enclosed pigsty is feasible and efficient.

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NUMERICAL SIMULATION OF A DOUBLE SKIN WITH SECONDARY VENTILATION FLOW ON ADIABATIC WALL

NUMERICAL SIMULATION OF A DOUBLE SKIN WITH SECONDARY VENTILATION FLOW ON ADIABATIC WALL

Rayleigh number the author founds a fully developed regime in which all the fluid entering from below exits through the top of the channel with a profile similar to that of Poiseuille. However, for high Rayleigh number, a boundary layer is observed near the heated wall; the fluid simultaneously enters from below and exits through the top of the channel via a reversed flow along the unheated wall. Aung et al. (1972) highlighted also two regimes in a numerical study concerning a natural convection induced flow in a channel heated symmetrically or asymmetrically: the first is developed at low Rayleigh numbers and the second is of boundary layer type for high Rayleigh numbers. Azevedo and Sparrow (1986) interested in the heat transfer intensification in natural convection flows in a vertical plane channel by studying the influence of the opening on the unheated wall. In this configuration, it has been shown that the average Nusselt number on the heated wall is almost independent of the location and size of the opening.

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Solutions for Energy Conservation and Pollution Reduction: Earth-Air Heat Exchangers

Solutions for Energy Conservation and Pollution Reduction: Earth-Air Heat Exchangers

In this perspective, the use of geothermal heat exchangers for heating and/or cooling of buildings has experienced lately a growing interest. Among these equipments, the earth-air heat exchangers (EAHXs) represent the simplest technical solution. Despite its simplicity (in fact, this is an advantage from all points of view: execution, maintenance, payback, etc.), earth-air heat exchangers lead to important energy savings concerning fresh air supply within ventilation systems of buildings during all the year [6]. Consequently, the objective of this study is to fulfill methodical numerical investigation in order to quantify energy and GES emissions savings, achieved by using earth-air heat exchangers added to ventilation systems for Romanian conditions (climate and typical dwelling built up according to national standards).

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Ventilation Solutions in Renovated  Apartment Buildings in Cold  Climate Conditions

Ventilation Solutions in Renovated Apartment Buildings in Cold Climate Conditions

mand, between 30% - 60% for new and retrofitted buildings [2]. As the ventilation heating demand plays an important role in the building’s total heating demand, the exhaust air heat recovery is inevitable. It is possible to recover only sensible heat or both sensible and latent heat from the exhaust air [3]-[5]. Energy is used to cover the heat losses due to ventilation air and to move the ventilation air for mechanical ventilation. The main pur- pose of the study is to compare the different ventilation solutions of apartment buildings and assess their energy consumption.

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Air Conditioning Design for a Small Hotel Dining Area

Air Conditioning Design for a Small Hotel Dining Area

1) Effective System Zoning: A HVAC system can be controlled via a single-zone strategy or a multi-zone strategy. With a single zone strategy, all areas served by the system receive the same amount of heating, cooling or air conditioning as defined by the control logic of the unit. However, different areas can have different energy requirements depending on a number of factors as outlined in section 2 above. Areas with similar end energy use requirements should be grouped and served from the same HVAC system. This will ensure the optimum amount of heating, cooling or ventilation is provided to the spaces when required. 2) Waste-Heat Recovery: Waste-heat recovery devices recover thermal energy from exhaust air and transfer it to the incoming

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Measuring thermal performance in steady state conditions at each stage of a full fabric retrofit to a solid wall dwelling

Measuring thermal performance in steady state conditions at each stage of a full fabric retrofit to a solid wall dwelling

Doors UPVC of amid range type, again typical of a 1980’s replacement (uninsulated timber doors units with single glazing were present during the preliminary experiment). Party wall Solid wall – same as external walls, except unplastered on the Guard House side. The environmental chamber is a large reinforced concrete structure. The chamber walls are insulated with 100 mm PIR foam insulation to the walls and ceiling and 35 mm expanded polystyrene insulation to the floor element (reinforced concrete slab on short bored piles). The chamber has the ability to maintain a constant temperature between the range -12 °C and +30 °C with an accuracy of ±0.5 °C at a 5 °C set-point. The chamber is cooled by an air handling unit that is supplied with cooling by four condenser units, with a total of 60 kW of cooling (15 kW per unit). This is supplied to the chamber via a ducted heating, ventilation, and air conditioning (HVAC) system. This system reacts to the heat load of the house in the chamber and maintains a set-point of ± 0.5 °C.

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Optimization of building integrated photovoltaic thermal air system combined with thermal storage

Optimization of building integrated photovoltaic thermal air system combined with thermal storage

Photovoltaic (PV) combined with phase change material (PV/PCM) system is a hybrid solar system that uses a PCM to reduce the PV temperature and to store energy for other applications. This study aims to increase the integrated PV efficiency of buildings by incorporating PCM while utilizing the stored heat in PCM for controlling indoor conditions. Experiments have been carried out on a prototype PV/PCM air system using monocrystalline PV modules. Transient simulations of the system performance have also been performed using a commercial computational fluid dynamics package based on the finite volume method. The results from simulation were validated by comparing it with experimental results. The results indicate that PCM is effective in limiting temperature rise in PV device and the heat from PCM can enhance night ventilation and decrease the building energy consumption to achieve indoor thermal comfort for certain periods of time. Keywords: photovoltaic; phase change material; hybrid solar; BIPV

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Factors affecting greenhouse microclimate and its regulating techniques: a review

Factors affecting greenhouse microclimate and its regulating techniques: a review

The design parameters and the selection of microclimate control techniques are vital for sustainable greenhouse farming in the regions of adverse climatic conditions. This paper therefore reviewed the factors influencing the microclimate of the greenhouse and the latest advance in technology for regulating the microclimate of the greenhouse. The influence of greenhouse design parameters and its functional characteristics on microclimate of greenhouse was reviewed in terms of its shapes and orientations, the wind direction, the selection of covering materials and the effects of insect-proof screen. The importance of natural ventilation was stressed and the recommend location of opening vents and the ratio of ventilation area/surface roof area were summarized. The performance of evaporative cooling including pad-fan system, misting/fogging system and roof sprinkler system was discussed. The advantages of earth to air heat exchanger and the heat storage method using phase change material were introduced which can be used for heating or cooling throughout the year. The above knowledge offers insights for the design and selection of regulating techniques for advancing greenhouse applications in southeast China’s Ningbo area with low technology structures. In the future, we will carry out further comparison and investigation of the reviewed microclimate regulating techniques to find out suitable solutions for local greenhouse farming.

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The Efficiency Analysis of the Exhaust  Air Heat Pump System

The Efficiency Analysis of the Exhaust Air Heat Pump System

When installing the exhaust air heat pump system in an old building, pre-conditions have to be met, without which it is not possible to ensure effective work of the system and indoor climate that satisfies requirements. The heating system of the building has to be adjusted to a low temperature heating graph, the recommended graphs are 55/40 or up to 60/40, because the heat pump works more effectively at a low temperature. There should be no towel dryers before the water extraction devices in the domestic hot water system, so that the hot water temperature would not have to be higher than 55 ˚C. The consumption analysis performed during a year showed that the exhaust air heat pump is able to produce heat according to the amount of exhaust air flow in these conditions (the air flow rate, indoor air temperature, heat transfer, efficiency of the device) producing heat pursuant to the amount of the exhaust air flow. The use of the exhaust air heat pump is more effective if, in addi- tion to granting heat energy to the heating system, it can also be used for producing domestic hot water. In apartment buildings with the conventional mechanical exhaust ventilation system, the indoor climate is good. However, studies show that in those apartment buildings it is reasonable to use the exhaust air heat pump for energy conservation.

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Urban Landscape Challenges and Mitigation Proposal for Metropolitan City

Urban Landscape Challenges and Mitigation Proposal for Metropolitan City

In warm humid areas windows should be large and fully open able, with inlets of a similar size on both sides of the room allowing a proper cross-ventilation. Door shutters also incorporate louvers or grills. Windows should be at both windward and leeward walls. It is a good precedent to have windows on the adjacent walls for good ventilation with building side perpendicular to the wind but a tilt of 20 to 30 degrees from perpendicular will not weaken interior ventilation. As per experiments conducted the wind at an incidence angle of 45 degrees reduces when the interior velocities to be 15-20 percent lower than when wind perpendicular to the inlet. When the windows are on opposite walls, a 45-degree incidence angle gives the maximum average indoor air velocity and better distribution of indoor air. For windows only on one side of the wall, vertical projections called as wing walls can create artificial pressure and suction zones for improving ventilation on the windward side of the building. Unequal inlet and outlet sizes can induce higher air velocities. Casement windows allow for larger opening size are better than Sliding windows louvered windows and pivot windows as they reduce the opening sizes. The use of glass for windows and openings will need sunshades for in reducing heat gain, reduce solar glare, provide rain protection for opening windows, and to serve as part of a maintenance strategy. Shading devices should be much larger to provide great coverage, obstructing most of options from the conventional horizontal, vertical, or egg crate projections, and more advanced technique are Automated (linked to daylight sensors and/or sun tracking systems) shading devices should be exploited and selected as best suited to design and budget .

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Development of Generalize Software to Estimate Cooling Load for Air Conditioning Multi Storey Buildings In C++

Development of Generalize Software to Estimate Cooling Load for Air Conditioning Multi Storey Buildings In C++

------------------------------------------------------------------------***------------------------------------------------------------------------- Abstract: In India just as much energy if not more may be used for cooling in summer the actual cooling load for multi storey building during peak load period of the month April. With large building such commericial complex auditorium,office buildings are provided with central air conditioning system.The effective design of central air conditioning can provide lower power consumption capital cost and improve aesthetics of a building. Cooling load items such as lighting heat gain,people heat gain, infiltration and ventilation heat gain can easily be putted to the computer program and find the output.The aim of this paper is to develop generally software for air conditioning system to estimate total cooling load for any rooms , lecture halls, offices of any Multi Storey buildings. In this research paper we consider a lecture hall of Baba Saheb Dr. Bhim Rao Ambedkar College of agricultural Engineering and Technology Etawah (206001) which is a part of institution. Institution is a Multi Storey building.The calculation of the total cooling load for only the lecture hall by CLTD method and also develop the software of this calculative load by flowchart of the software for the lecture hall. Similarly this procedure apply to find total cooling load of every room, halls, offices by this software in Institution and find the size of air conditioning system in every rooms, halls, offices, practical labs in institution.

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Development of Generalize Software to Estimate Cooling Load for Air Conditioning Multi Storey Buildings In C++

Development of Generalize Software to Estimate Cooling Load for Air Conditioning Multi Storey Buildings In C++

------------------------------------------------------------------------***------------------------------------------------------------------------- Abstract: In India just as much energy if not more may be used for cooling in summer the actual cooling load for multi storey building during peak load period of the month April. With large building such commericial complex auditorium,office buildings are provided with central air conditioning system.The effective design of central air conditioning can provide lower power consumption capital cost and improve aesthetics of a building. Cooling load items such as lighting heat gain,people heat gain, infiltration and ventilation heat gain can easily be putted to the computer program and find the output.The aim of this paper is to develop generally software for air conditioning system to estimate total cooling load for any rooms , lecture halls, offices of any Multi Storey buildings. In this research paper we consider a lecture hall of Baba Saheb Dr. Bhim Rao Ambedkar College of agricultural Engineering and Technology Etawah (206001) which is a part of institution. Institution is a Multi Storey building.The calculation of the total cooling load for only the lecture hall by CLTD method and also develop the software of this calculative load by flowchart of the software for the lecture hall. Similarly this procedure apply to find total cooling load of every room, halls, offices by this software in Institution and find the size of air conditioning system in every rooms, halls, offices, practical labs in institution.

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