Damper section

Damper section A section of HVAC equipment containing a damper or valve. 

Dampers in air handling units and air distribution systems Attention has to be paid to reducing the leakages, in accordance with EN 1751. Dampers used in mixing sections of air-handling units must fulfill additional requirements, in accordance with prEN 13053. 

Mixing section of an ATD A section in which two air streams of different temperatures or moisture content are damper controlled to provide a given flow rate before mixing occurs. 

This specialized form of supply air system is often used in large open industrial spaces. It comprises a modular system of components that can be built up into simple systems. A typical system might have a roof inlet cowl, a recirculation damper, a heater battery, a fan, one or two outlet grilles and short sections of connecting ductwork, and would handle airflows up to 3-4m /s, depending on size. A number of individual systems would be used to provide the total airflow required in the space (Figure 28.4). Systems are normally manufactured with aluminum casings to reduce the roof load. 

With air-cooled condensers and water cooling towers it is possible to reduce the air flow hy automatic dampers, fan speed control, or switching off fans, where two or more drives are fitted. The control should work from pressure hut can he made to work from temperature (see Section 6.12). 

The exit gas section contains the air heater tube bundles, flue gas dampers, and the various emission control systems such as dust collectors, electrostatic precipitators, and gas scrubbers. 

It is normal practice to operate with a slight vacuum throughout the heater, so that air will leak in through sight-boxes and dampers, rather than combustion products leak out. Typically, the aim would be to maintain a vacuum of around 2 mm water gauge just below the convection section. 

Figure 3.4 — (A) FIA manifold for the determination of L-lactic acid in milk products P peristaltic pump C carrier S sample V injection valve AD air damper FTC flow-through cell W waste BFB bifurcated fibre LS light source PMT photomultiplier tube R recorder. (B) Cross-section of lactic acid optrode. (Reproduced from [39] with permission of VCH Publishers).

The regulation dampers — air flow (blow, return, or exhaust) by room or by intake or return opening — must be manual with mechanical locking (minimal looseness allowed) located in the ducts. The general dampers, or those for most important sections, must be similar to the dampers for air handling unit a suitable model should be selected. 

In all cases, to achieve a proper regulation of the flow, a pulsation damper is used. It operates on the principle of a mechanical ballast or can be electronically controlled. The simplest mechanical ballasting device is a coil with a low cross-section, several metres in length, placed between the pump and the injector. Under the influence of a wave of solvent, the tube uncoils slightly which increases its internal volume and dampens the variation in pressure. 

The air register and the stack damper are used together as a team to optimize the heater draft. Our aim in balancing the draft for a natural-draft or a balanced-draft heater is to maintain a small negative pressure of, say, —0.2 to —0.1 in of water, just below the shock tubes (please refer to Fig. 20.5), at the entrance to the convective section. At the same time we must maintain enough air to operate on the good side of the point of absolute combustion. 

As we close the stack damper, the pressure at the convective-section inlet will increase that is, we will have less draft. This will reduce the rate of flue gas then to the convective section, minimizing the rate of air in-leakage to the convective section and the chances of afterbum occurring. However, if we close the stack damper too much, a positive pressure will develop at the convective-section inlet, which we must avoid. 

Suppose we put the air registers back as they were and pinch on the stack damper instead. So let s suppose we restrict airflow via the stack damper until the firebox oxygen goes down from our base case value of 6 percent, to 3 percent. The oxygen in the convective section will also be reduced to, say, 5 percent. In this case, we see that the A02 is also much... 

The principal design feature that permits economical application of the wet/dry tower is the summer damper component. This is a door-like air flow restrictor that is located in the heated dry air stream between the air-cooled heat exchanger and the fan. Its purpose is to reduce the air flow through the dry stream, while boosting the air flow in the wet stream, thereby enhancing the wet section thermal performance during summer operation. 

Shaker filters have the drawback that they must be taken off stream to clean the bags. Since continuous on stream operation is required, several baghouse chambers are installed in parallel with dampers, permitting one section to be in the cleaning cycle while the rest of the baghouse is filtering the dust-laden gas stream. 

Minimize accumulations of condensed liquids. Balance airflow without dampers to prevent unwanted change of airflow rates, and eliminate accumulations of condensed liquids and solids. Provide air-cleaning devices (air filters, scrubbers, etc.) with protection measures against the consequences of gas explosions (refer to the section titled Protective Measures ). 

This section has shown that ambient conditions can significantly impact NO, and CO emissions. Tight control of burner operating condifions is essenfial to minimize these emissions. This can be done in two ways manual or automatic control. Manual control means that operators must frequently adjust dampers (air registers) on every burner as ambient conditions change. It is not enough to adjust only some of fhe burners to... 

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