Cooling load

Cooling loads can be transferred from process heat exchangers to a wastewater-evaporation system, thus reducing cooling-water requirements and total wastewater volume. 

Example 5 Cooling and Dehumidification Find the cooling load per pound of dry air resulting from infiltration of room air at 80 F dry-bulb temperature and 67 F wet-bulb temperature into a cooler maintained at. 30 F dry-bulb and 28 F wet-bulb temperature, where moisture freezes on the coil, which is maintained at 20 F. 

Note that if the enthalpy deviations were ignored, the calculated cooling load would be about 5 percent low. 

Heating and cooling load calculation for HVAC system design is based on the heat balance principle. For the given building, room, or independent building zone, heat balance components should be established and analyzed. The ma or heat sources and sinks in industrial buildings are ... 

As the outside air conditions vary from hour to hour, day to day, and month to month, to economize on the heating and cooling loads, the recirculated and fresh airsrreams are mixed in varying proportions. If the air contains toxic or inflammable gases, vapors, or dusts, no direct mixing occurs, and a hcat-tccovery device is used. 

A workshop is30mxl5mx4m and has to be maintained at 20 C with six air changes per hour with a supply air temperature of 14 C. Determine the maximum cooling load that can be met. 

Outdoor air humidity strongly affects the latent cooling load and energy requirements during summer season. Year-round outdoor air humidity must be considered when studying condensation conditions. 

Santamouris M. NORMA—a method to calculate the thermal performance of passively cooled buildings. Cooling loads of buildings, vol. 5. Dublin School of Architecture, University College Dublin, 19.94. 

Standard SIA V 382/2 Determination of the cooling load demand of buildings [in German]. Zurich SIA (Swiss Engineers and Architects Association), 1992. 

Cooling load The quantity of heat to be removed from a process or a space in order to meet the plant design or environmental conditions. 

Cooling load, latent The quantity of heat to be extracted from a medium, without temperature change, in order to produce a given mass of fluid or condensate from the vapor. 

Cooling load, sensible The quantity of hear to be removed from a fluid stream to maintain a desired fluid temperature. 

Load factor The ratio of the average demand to the maximum demand may relate to electrical, heating, or cooling load. 

Ventilation thermal load The heating or cooling load required to compensate for thermal losses resulting from natural or mechanical ventilation. 

Motion detectors and daylight detectors reduce artificial lighting use, reducing summer cooling loads. 

To save energy, many HVAC systems employ a mechanism for regulating the flow of outdoor air called an economizer cycle. An economizer cycle takes advantage of milder outdoor conditions to increase the outside air intake and in the process reduces the cooling load on the system. Controlling the rate of flow of outdoor air appears simple, in theory, but often works poorly m practice. The small pressure drop required to control the flow rate of outdoor air is rarely controlled and monitored. Quite often, the damper system used to regulate the airflow is nonfunctional, disconnected from the damper actuators, or casually adjusted by building operators (Institute of Medicine, 2000). 

The impact of incorrect equipment sizing practices is magnified in an energy-efficient home that has dramatically reduced heating and cooling loads. 

Besides increasing systemwide cooling loads, summer heat islands increase smog production. Smog... 

Almost all commercial buildings are cooling-dominated, and solar gains through windows are major contributors to cooling loads. 

Cooling loads are most significant on hot summer afternoons when electric utilities typically have annual peak loads. Lower solar heat gains lead to reduced peaks, which reduce peak demand charges and power plant capacity requircliiclits. 

If the temperature is too high, an expensive tower will be specified and of course, if too low, the cooling load service will be required to sacrifice performance during the times when the wet bulb exceeds the specified value. At constant inlet humidity and constant rates for liquid, L, and air, G, the effect of changing wet bulb on the performance factor KaV/L is only 1.2% with no trend dependent on rates [38]. 

A building or process having a large number of separated cooling loads could have a refrigeration system for each of these loads. It will usually be more convenient to concentrate the cooling into one plant. 

Variations in cooling load can be provided from the latent heat of melting of ice or a frozen eutectic. Ice can be formed by allowing it... 

To handle a peak cooling load with a reduced size of refrigeration plant, typically to make ice over a period of several hours and then use ice water for the cooling of a batch of warm milk on a dairy farm. This is also used at main creameries, to reduce peak electricity loads. The available water is very close to freezing point, which is the ideal temperature for milk cooling. 

The rate of heat extraction, i.e. the product cooling load, will he Q = H/1 where t = the time available for cooling. 

Example 21.6 A dockside frozen meat store has a capacity of 1000 t stored at - 12°C, and leaving the store at a maximum rate of 50 t/day. Meat may arrive from a local abattoir at 2°C or from ships in batches of 300 t at - 10°C. Estimate a product cooling load. 

Meat goes out at the rate of 350 t/week and may arrive from local supplies. There is possibly a four-day week, allowing for odd holidays, and so there may be 90 t/day from the abattoir. Cooling load is 90 t/day from 2°C to - 12°C. Tables give the following ... 

Example 21.8 The meat-cooling load in Example 21.2 is probably a daily batch from an abattoir and the duty will be less at night, once the meat is cooled. The maximum capacity will therefore be 10.3 kW, plus the fans and other room losses, and the plant will run continuously while the meat is being chilled only. 

Product cooling load, from Example 21.6 case 3. Allow another 5% for higher ambient, in case meat warms up in transit from abattoir =153 kW... 

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