Heat, ventilation and air-conditioning development

For many years the development of heating, ventilation and air-conditioning as three branches of engineering, which are closely connected was given a major share of attention to. They are concerned with providing a required atmospheric environment within a space, heating with respect to heat supply to produce a desired temperature for maintaining comfort, health and efficiency comfort, ventilation with regard to supply and re­moval of the air, air-conditioning implies the control of temperature, hu­midity, purity, motion of the air in an enclosure.

In our modern world three branches of engineering, which are highly developed are of great significance for industrial processes as well as for human comfort.

Scientific research has established certain standards of maximum comfort for the atmospheres within a room. Different experiments have led engineers to fruitful results in the proper choice of HPAC systems.

Packaged units, field -erected types of equipment, multizone de­vices, filters, preheat and cooling coils, fans and controls are widely in-stalled in industrial, office and residential buildings. No factory, school, plant, hospital, large recreation halls are possible without unit air-conditioners and window ventilators.

Tests are carried out on the noise level and power consumption of electric motors, ventilation control system and thermostatic controls. Basic flame characteristics and combustion chemistry, the flow of gases and the characteristics for fans and motors are some of the aspects studied in heat research, while in ventilation; the laboratory is constantly examining the whole field of aerodynamics and its relation to the movement of air.

There are certain industrial processes that are accompanied by the production of air-born dust fumes, toxic vapoures and gases which arc hazardous to the health of workers, so HPAC is to be further developed having a wide range of application.

FANS

Fans are used extensively in the heating and ventilating industry and in most power plants. Their basic design principles fall into two classes: ax­ial-flow fans and centrifugal or radial-flow fans. Axial-flow fans arc basically rotating air-flow sections similar to the propeller of an airplane.

The simplest axial-flow fan is the small electric fan used for circulat­ing air in rooms against very little resistance. Axial-flow fans for industrial purposes are the two-blade or multi-blade propeller type, and the multi-blade air-foil type. Air enters the fan suction from the left and flows over the rotor with a minimum of turbulence owing to the streamline form of the rotor and drive mechanism. The air stream is straightened by guide vanes located on the discharge side, thus decreasing the rotational energy of the air by converting it to energy of translation.

The axial-flow fan operates best under conditions where the resistance of the system is low, as in the ventilating field. The axial-flow fan occu­pies a small space is light in weight, is easy to install, and handless large volumes of air.

Centrifugal fans may be divided into two major classes:

1)the long-blade or plate-type fan,

2)the short-blade multi-blade fan.

The blades of either type may be pitched forward the direction of mo­tion of the fan, radially, or away from the direction of motion of the man.

A plate-type radial-blade rotor with double inlet is best suited for han­dling dirty gases, since there are no pockets in the blades to catch and collect the dirt. The rotor has wearing strips welded to the blades to increase their life. The fan is designed for induced-draft service. The housing of such a fan may have catch plates in the scroll face to collect the fly ash.