Vapor escape mechanism

FIGURE 15.64 Vapor escape mechanisms in pool boiling from cylinders, (a) small cylinder (b) large cylinder (c) cross section (from Lienhard and Dhir [155], with permission of ASME). 

For the hydrodynamic instability model, Lienhard and Dhir (1973b) extended the Zuber model to the CHF on finite bodies of several kinds (see Sec. 2.3.1, Fig. 2.18). Lienhard and Hasan (1979) proposed a mechanical energy stability criterion The vapor-escape wake system in a boiling process remains stable as long as the net mechanical energy transfer to the system is negative. They concluded that there is no contradiction between this criterion and the hydrodynamic instability model. 

In a 3-I. round-bottomed flask provided with a mechanical stirrer and a 90-cm. air-cooled condenser are placed 288 g. (3 moles) of freshly distilled furfural, 460 g. (425 cc., 4.5 moles) of acetic anhydride, and 294 g. (3 moles) of dry, pulverized, freshly fused potassium acetate (Note 1). The ingredients are mixed thoroughly, stirring is started, and the flask is heated in an oil bath at 150° (bath temperature) for four hours, without interruption (Note 2). It is well to make provision for acetic acid vapor which escapes through the air condenser. 

Apparatus A 125 cc. Erlenmeyer flask is provided with a one-hole rubber stopper fitted with a small bulb trap as show in Fig. 66. The trap is about 45 mm. high, and is made by sealing a short tube into a bulb about 25 mm. in diameter. It is filled with fused calcium chloride held in place by absorbent cotton. Its object is to prevent the loss of water vapor which might be carried off mechanically by the escaping carbon dioxide. The whole apparatus should not weigh more than 60 gm. before adding the acid... 

Division 2 locations are those where flammable liquids or gases are present but are normally confined and can escape only through accident or abnormal operation.. lso included are areas where ignitable concentrations of gases or vapors are normally prevented by mechanical ventilation, but might become hazardous because of failure or abnormal operation of the equipment. A third Division 2 situation is an area adjacent to a Division 1 location, where ignitable concentrations of gas or vapor might occasionally be communicated (unless ap-... 

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