Air-heating coils

A1.1.1 The body and cover of the cell shall be constructed of stainless steel and the air-heating coil of tinned copper tubing. 

FIG. 11 91 Effect of circulation ratio on the overall heat-transfer coefficient of an air-cooling coil. 

Example 3 Air Heating Air is heated by a steam coil from 30 F dry-bulb temperature and 80 percent relative humidity to 75 F dry-bulb temperature. Find the relative humidity, wet-bulb temperature, and dew point of the heated air. Determine the quantity of heat added per pound of dry air. 

Performance Data for Direct-Heat Tray Dryers A standard two-truck diyer is illustrated in Fig. 12-48. Adjustable baffles or a perforated distribution plate is normally employed to develop 0.3 to 1.3 cm of water-pressure drop at the wall through which air enters the truck enclosure. This will enhance the uniformity of air distribution, from top to bottom, among the trays. In three (or more) truck ovens, air-reheat coils may be placed between trucks if the evaporative load is high. Means for reversing air-flow direction may also be provided in multiple-truck units. 

Forced-convection pit furnaces are employed for heat-treating small metal parts in biuk. Small pieces are suspended in a mesh-bottom basket, while larger pieces are placed on racks. Air heating is by means of Nichrome electric coils set in refractory walls around the... 

Conveying-screen diyers are fabricated with conveyor widths from 0.3- to 4.4-m sections 1.6 to 2.5 m long. Each section consists of a sheet-metal enclosure, insulated sidew s and roof, heating coils, a circulating fan, inlet-air distributor baffles, a fines catch pan under the... 

The elements of a PM plan include periodic inspection, cleaning, and service as warranted, adjustment and calibration of control system components, maintenance equipment and replacement parts that are of good quality and properly selected for the intended function. Critical HVAC system components that require PM in order to maintain comfort and deliver adequate ventilation air include a outdoor air intake opening, damper controls, air filters, drip pans, cooling and heating coils, fan belts, humidification equipment and controls, distribution systems, exhaust fans. 

Verntal supply Local Convective Air heating Fan coils Supply air cooling... 

The step change is close to the situation where the sensor is suddenly moved from one place to another having a different state of the measured quantity. The exponential change could, for example, be the temperature change of a heating coil or some other first-order system. Finally, the velocity fluctuations of room air can be approximated with a sine or cosine function. 

Air heating and cooling coil As tube or plate heat exchanger in which air, the secondary fluid, is either heated or cooled with a primary medium. 

Preheat coil A heating coil in a ductwork run sized either to temper the air or to stop the filter from freezing. 

Mass transfer may take place from a mixture of gases, such as the condensation of water from moist air. In this instance, the water vapour has to diffuse through the air, and the rate of mass transfer will depend also on the concentration of vapour in the air. In the air-water vapour mixture, the rate of mass transfer is roughly proportional to the rate of heat transfer at the interface and this simplifies predictions of the performance of air-conditioning coils [1,5, 9]. 

Example 24.1 Air circulates at the rate of 68 kg/s and is to be heated from 16°C to 34°C. Calculate the heat input and the water mass flow for an air heater coil having hot water entering at 85°C and leaving at 74°C. 

Winter heating items fitted within room air-conditioners may be electric resistance elements, hot water or steam coils, or reverse cycle (heat pump). One model of water-cooled unit operates with a condenser water temperature high enough to be used also in the heating coil. 

The most advantageous application of the heat pump in the UK at the present time is where air cooling is required in the summer and air heating from the same piece of equipment in the winter. The alternatives will be electric resistance heating, with a higher fuel cost, or the provision of a hot water coil, at extra capital cost. 

Example 35.6 An air cooling coil extracts 45 kW sensible heat with air entering at 24°C and leaving at 18°C, with the refrigerant evaporating at 11°C. Estimate the cooling capacity at 95, 90 and 85% mass air flow. 

Ethanoiamine is used to absorb carbon dioxide. A tank that contained the absorption product combusted spontaneously in air, probably because of an unknown impurity and because an amine evaporation had stripped a heating coil of this compound. The fire went out later due to the carbon dioxide release caused by the compound s temperature rise. 

The first ground-source heat pump was installed in Indianapolis, Indiana in the home of Robert C. Webber, an employee of the Indianapolis Power and Light Company. It was a 2.2 kW compressor hooked to a direct expansion ground coil system in trenches supplying heat to a warm air heating system. The installation was monitored beginning October 1, 1945 and this is the first day of ground source heat pump operation documented in literature [2],... 

Space savings arising from the smaller size of boiler and cooling tower is offset by the addition of central heat pump. Use of fan coil units at the zone level is not expected to result in space savings because of larger requirement of air flow arising from lower temperature difference across the heating coil. 

The equipment operates by negative pressure differential generated by a turbine. Air is drawn in the inlet duct, throttled at the inlet flap, cleaned at the inlet filter, heated at the steam heated coils, and then used to fluidize the material resting on the screen in the bottom of the product bowl. The air is then cleaned at the outlet filter, throttled at the outlet flap, and accelerated through the turbine to the atmosphere. 

If air of humidity M is passed over heating coils so that its temperature rises to 9, this operation may be represented by the line AB on the humidity chart shown in Figure 16.8. This air then passes over the wet material and leaves at, say 90 per cent relative humidity,... 

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