Cooling Tower Design Calculation Software

• Fans: for air circulation and ventilation. • Chillers: for the production of chilled water for large buildings (note: for small buildings use the direct expansion cooling systems such as packaged air-conditioners). • Boilers: for the production of hot water for Heating (note: it is often to use the electric heaters for zonal reheat). • Pumps: for the circulation of heating hot water, chilled water and condenser water. • Cooling towers: for heat rejection.

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The primary energy use is the cooling tower fan and pumps. • Controls: coordinate the operation of the mechanical components together as a system. • A chiller is a mechanical refrigeration device, like an air conditioner, except that it cools a fluid (usually water) instead of cooling air. • When a large air conditioner is required it is sometimes more feasible to use one large chiller instead of many small air conditioners. • Chillers are also used wherever there is a need for cooling a fluid such as a chemical process or for plastics molding. • To simplify the concept of a chiller you should compare it to a drinking fountain where you get cold “chilled” water.

• There are a variety of water chiller types (see Fig.2 ). Most commonly, they are absorption, centrifugal, helical rotary, and scroll. Some reciprocating chillers are also available.

Within This Page • • • • Almost all historic buildings were ventilated naturally, although many of these have been compromised by the addition of partition walls and mechanical systems. With an increased awareness of the cost and environmental impacts of energy use, natural ventilation has become an increasingly attractive method for reducing energy use and cost and for providing acceptable and maintaining a healthy, comfortable, and rather than the more prevailing approach of using mechanical ventilation. In favorable climates and buildings types, natural ventilation can be used as an alternative to air-conditioning plants, saving 10%–30% of total energy consumption. Natural ventilation systems rely on pressure differences to move fresh air through buildings. Pressure differences can be caused by wind or the buoyancy effect created by temperature differences or differences in humidity. In either case, the amount of ventilation will depend critically on the size and placement of openings in the building. It is useful to think of a natural ventilation system as a circuit, with equal consideration given to supply and exhaust.

Openings between rooms such as transom windows, louvers, grills, or open plans are techniques to complete the airflow circuit through a building. Code requirements regarding smoke and fire transfer present challenges to the designer of a natural ventilation system. For example, historic buildings used the stairway as the exhaust stack, a technique now prevented by code requirements in many cases. Description Natural ventilation, unlike fan-forced ventilation, uses the natural forces of wind and buoyancy to deliver fresh air into buildings.

Fresh air is required in buildings to alleviate odors, to provide oxygen for respiration, and to increase. At interior air velocities of 160 feet per minute (fpm), the perceived interior temperature can be reduced by as much as 5°F. However, unlike true air-conditioning, natural ventilation is ineffective at reducing the humidity of incoming air.

Silent Hill 2 Ps2 Iso Download Torrent more. This places a limit on the application of natural ventilation in humid climates. Types of Natural Ventilation Effects Wind can blow air through openings in the wall on the windward side of the building, and suck air out of openings on the leeward side and the roof. Temperature differences between warm air inside and cool air outside can cause the air in the room to rise and exit at the ceiling or ridge, and enter via lower openings in the wall. Similarly, buoyancy caused by differences in humidity can allow a pressurized column of dense, evaporatively cooled air to supply a space, and lighter, warmer, humid air to exhaust near the top. These three types of natural ventilation effects are further described below. Wind Wind causes a positive pressure on the windward side and a negative pressure on the leeward side of buildings. To equalize pressure, fresh air will enter any windward opening and be exhausted from any leeward opening.

In summer, wind is used to supply as much fresh air as possible while in winter, ventilation is normally reduced to levels sufficient to remove excess moisture and pollutants. An expression for the volume of airflow induced by wind is: Qwind = K x A x V, where Qwind = volume of airflow (m 3/h) A = area of smaller opening (m 2) V = outdoor wind speed (m/h) K = coefficient of effectiveness The coefficient of effectiveness depends on the angle of the wind and the relative size of entry and exit openings. It ranges from about 0.4 for wind hitting an opening at a 45° angle of incidence to 0.8 for wind hitting directly at a 90° angle.

Sometimes wind flow prevails parallel to a building wall rather than perpendicular to it. In this case it is still possible to induce wind ventilation by architectural features or by the way a casement window opens. For example, if the wind blows from east to west along a north-facing wall, the first window (which opens out) would have hinges on the left-hand side to act as a scoop and direct wind into the room. The second window would hinge on the right-hand side so the opening is down-wind from the open glass pane and the negative pressure draws air out of the room.

It is important to avoid obstructions between the windward inlets and leeward exhaust openings. Avoid partitions in a room oriented perpendicular to the airflow. On the other hand, accepted design avoids inlet and outlet windows directly across from each other (you shouldn't be able to see through the building, in one window and out the other), in order to promote more mixing and improve the effectiveness of the ventilation. Buoyancy Buoyancy ventilation may be temperature-induced (stack ventilation) or humidity induced (cool tower). The two can be combined by having a cool tower deliver evaporatively cooled air low in a space, and then rely on the increased buoyancy of the humid air as it warms to exhaust air from the space through a stack. The cool air supply to the space is pressurized by weight of the column of cool air above it.

Although both cool towers and stacks have been used separately, the author feels that cool towers should only be used in conjunction with stack ventilation of the space in order to ensure stability of the flow. Buoyancy results from the difference in air density. The density of air depends on temperature and humidity (cool air is heavier than warm air at the same humidity and dry air is heavier than humid air at the same temperature). Within the cool tower itself the effect of temperature and humidity are pulling in opposite directions (temperature down, humidity up). Within the room, heat and humidity given off by occupants and other internal sources both tend to make air rise. The stale, heated air escapes from openings in the ceiling or roof and permits fresh air to enter lower openings to replace it. Stack effect ventilation is an especially effective strategy in winter, when indoor/outdoor temperature difference is at a maximum.

Stack effect ventilation will not work in summer (wind or humidity drivers would be preferred) because it requires that the indoors be warmer than outdoors, an undesirable situation in summer. A chimney heated by solar energy can be used to drive the stack effect without increasing room temperature, and solar chimneys are very widely used to ventilate composting toilets in parks.

An expression for the airflow induced by the stack effect is: Qstack = Cd*A*[2gh(Ti-To)/Ti]^1/2, where Qstack = volume of ventilation rate (m 3/s) Cd = 0.65, a discharge coefficient. A = free area of inlet opening (m 2), which equals area of outlet opening.

G =9.8 (m/s 2). The acceleration due to gravity h = vertical distance between inlet and outlet midpoints (m) Ti = average temperature of indoor air (K), note that 27°C = 300 K. To = average temperature of outdoor air (K) Cool tower ventilation is only effective where outdoor humidity is very low. The following expression for the airflow induced by the column of cold air pressurizing an air supply is based on a form developed by Thompson (1995), with the coefficient from data measured. This tower is 7.4 m tall, 2.4 m square cross section, and has a 3.1 m 2 opening. Qcool tower =0.49 * A* [2gh (Tdb-Twb)/Tdb]1/2, where Qcool tower = volume of ventilation rate (m 3/s) 0.49 is an empirical coefficient calculated with data from Zion Visitor Center, UT, which includes humidity density correction, friction effects, and evaporative pad effectiveness.

A = free area of inlet opening (m 2), which equals area of outlet opening. G =9.8 (m/s 2). The acceleration due to gravity h = vertical distance between inlet and outlet midpoints (m) Tdb = dry bulb temperature of outdoor air (K), note that 27°C = 300 K. Twb = wet bulb temperature of outdoor air (K) The total airflow due to natural ventilation results from the combined pressure effects of wind, buoyancy caused by temperature and humidity, plus any other effects from sources such as fans. The airflow from each source can be combined in a root-square fashion as discussed in. The presence of mechanical devices that use room air for combustion, leaky duct systems, or other external influences can significantly affect the performance of natural ventilation systems.

Design Recommendations The specific approach and design of natural ventilation systems will vary based on building type and local climate. However, the amount of ventilation depends critically on the careful design of internal spaces, and the size and placement of openings in the building. • Maximize wind-induced ventilation by siting the ridge of a building perpendicular to the summer winds. • Approximate wind directions are summarized in seasonal 'wind rose' diagrams available from the. However, these roses are usually based on data taken at airports; actual values at a remote building site can differ dramatically. • Buildings should be sited where summer wind obstructions are minimal.

A windbreak of evergreen trees may also be useful to mitigate cold winter winds that tend to come predominantly from the north. • Naturally ventilated buildings should be narrow. Download Proxy Server there. • It is difficult to distribute fresh air to all portions of a very wide building using natural ventilation. The maximum width that one could expect to ventilate naturally is estimated at 45 ft. Consequently, buildings that rely on natural ventilation often have an articulated floor plan. • Each room should have two separate supply and exhaust openings.

Locate exhaust high above inlet to maximize stack effect. Orient windows across the room and offset from each other to maximize mixing within the room while minimizing the obstructions to airflow within the room. • Window openings should be operable by the occupants. • Provide ridge vents. • A ridge vent is an opening at the highest point in the roof that offers a good outlet for both buoyancy and wind-induced ventilation. The ridge opening should be free of obstructions to allow air to freely flow out of the building.

• Allow for adequate internal airflow. • In addition to the primary consideration of airflow in and out of the building, airflow between the rooms of the building is important. When possible, interior doors should be designed to be open to encourage whole-building ventilation. If privacy is required, ventilation can be provided through high louvers or transoms. • Consider the use of clerestories or vented skylights. • A clerestory or a vented skylight will provide an opening for stale air to escape in a buoyancy ventilation strategy. The light well of the skylight could also act as a solar chimney to augment the flow.

Openings lower in the structure, such as basement windows, must be provided to complete the ventilation system. • Provide attic ventilation. • In buildings with attics, ventilating the attic space greatly reduces heat transfer to conditioned rooms below. Ventilated attics are about 30°F cooler than unventilated attics.

• Consider the use of fan-assisted cooling strategies. • Ceiling and whole-building fans can provide up to 9°F effective temperature drop at one tenth the electrical energy consumption of mechanical air-conditioning systems. • Determine if the building will benefit from an open- or closed-building ventilation approach.

• A closed-building approach works well in hot, dry climates where there is a large variation in temperature from day to night. A massive building is ventilated at night, then, closed in the morning to keep out the hot daytime air. Occupants are then cooled by radiant exchange with the massive walls and floor.

• An open-building approach works well in warm and humid areas, where the temperature does not change much from day to night. In this case, daytime cross-ventilation is encouraged to maintain indoor temperatures close to outdoor temperatures. • Use in hot, humid climates. • Try to allow at night in hot climates. • Open staircases provide stack effect ventilation, but observe all fire and smoke precautions for enclosed stairways.