Heat gains

Product temperature above space temperature (resulting in a heat gain to the space)... 

Product temperature below space temperature (producing a credit to sensible-heat gain or a heating requirement)... 

Water vapor from moist product Sensible and latent heat gains People... 

The ice crystals must be separated from the saline solution surrounding them, and washed with freshwater. This is accompHshed by a downward countercurrent flow of a small amount of freshwater through the ice slurry in the washer—melter unit. Keeping that unit at about 0°C limits the needed pressure rise by the compressor to only about 130—260 Pa, and an auxiUary refrigerator is often used to compensate for heat gains from the ambient and the compression. 

Commercial appHcations of calcium chloride and its hydrates exploit one or more of its properties with regard to aqueous solubiUty, hygroscopic nature, the heat gained or lost when one hydrated phase changes to another, and the depressed freezing point of the eutectic solution at a composition of about 30% by weight calcium chloride. 

Architectural Glass. The other important commercial glass-platiag appHcation is for production of architectural reflective glasses. Translucent metal films are used for decoration and for reduction of environmental heat gain. Electroless plating is used by one producer for this type of product (48). 

Relative humidity, percent = 50 Wind velocity, mi/h = 5 Dry-bulb air temperature, °F = 68 Solar heat gain, Btu/(h-ft ) = 100 Water quantity, gal/min = 10,000... 

The second context is the process reac tor. There is a potential for a runaway if the net heat gain of the system exceeds its total heat loss capabihty. A self-heating rate of 3°C/day is not unusual for a monomer storage tank in the early stages of a runaway. This corresponds to 0.00208°C/min, 10 percent of the ARC s detection limit. ARC data for the stored chemical would not show an exotherm until the self-heating rate was 0.02°C/min. Therefore, onset temperature information from ARC testing must be used with considerable caution. 

The part of the bus enclosure installed outdoors is exposed to solar radiation which is a cause of additional heat gain by the enclosure. ANSI C-37.24 has provided a basis to determine its effect in terms of heat generated as follows ... 

The continuous current rating of a bus system can be defined by the current at which a steady-state thermal condition can be reached. It is a balance between the enclosure and the conductor s heat gain and heat loss. If this temperature is more than the permissible steady-state thermal limit it must be reduced to the desired level by increasing the size of the conductor or the enclosure or both, or by adopting forced cooling. Otherwise the rating of the bus system will have to be reduced accordingly. 

Outdoor air is generally less polluted than the system return air. However, problems with reentry of previously exhausted air occur as a result of improperly located exhaust and intake vents or periodic changes in wind conditions. Other outdoor contamination problems include contaminants from other industrial sources, power plants, motor vehicle exhaust, and dust, asphalt vapors, and solvents from construction or renovation. Also, heat gains and losses through the building envelope due to heat conduction through exterior walls, floor, and roof, and due to solar radiation and infiltration, can be attributed to effects from external sources. 

Heat gains from processes with conversion of mechanical energy into heat... 

Heat gains and losses for heating or cooling raw materials and parts brought into or taken out of the building, melted metal solidification, vapor condensation, or liquid evaporation... 

The total heat gains and losses, AW, which should be compensated by the FIVAC system, can be determined by... 

Heat gains and losses can be only sensible or sensible and latent. Sensible heat gains result from conduction, convection, and/or radiation. Latent heat gains occur when moisture is added to the space fe.g., from evaporation . 

The total unit heat gain from the process equipment, can he evaluated using the graph in Fig. 7.1. 

Heat Gain from Equipment Operated by Electric Motors... 

Heat gain related to electric motors is calculated as ... 

The ventilation system can be used to full advantage during the summer months with the heater off to provide outside air and assist in removing the heat gains. 

Air-conditioning systems make use of this method, as the cooler, dense air supplied from high level will drop to low level, picking up the space heat gains before extraction at low level. 

Heat gained or lost by stream A = Heat gained or lost by stream B... 

In the case of summer cooling, the heat balance is Heat gain to space... 

Sensible heat gain (kW) = Air mass flow x Gain in specific enthalpy. 

The sensible heat gain is determined by taking into account all the heat gains in a space, such as solar, fabric, infiltration, machines, processes, occupancy, lighting, etc. 

In order to determine the summer supply air temperature for a given volume of air necessary to remove a given sensible heat gain, the following equation is used. 

The air temperature of a room at any given time is given hy a heat-balance equation which includes the heat flux exchanged by convection at each wall element (A q ), the heat flow exchanged by ventilation (4>j,), the convective part of heat flow due to internal heat gains the convective part of heat flow due to the HVAC system (< >[,(.), and the variation of energy in the room air(r M ... 

Heat gains from internal loads normally are sensible beat. Nevertheless, many processes release a significant amount of moisture. Also, occupants produce relevant amounts of latent heat, especially at high metabolic rates and at high air temperatures. 

Internal heat gains in conditioned spaces (casual gains)... 

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