Pumps temperature rise

Prepare two solutions, one containing i g. of diphenylamine in 8 ml. of warm ethanol, and the other containing 0-5 g. of sodium nitrite in i ml. of water, and cool each solution in ice-water until the temperature falls to 5°. Now add o 8 ml. of concentrated hydrochloric acid steadily with stirring to the diphenylamine solution, and then without delay (otherwise diphenylamine hydrochloride may crystallise out) pour the sodium nitrite solution rapidly into the weil-stirred mixture. The temperature rises at once and the diphenylnitrosoamine rapidly crystallises out. Allow the mixture to stand in the ice-water tor 15 minutes, and then filter off the crystals at the pump, drain thoroughly, wash with water to remove sodium chloride, and then drain again. Recrystallise from methylated spirit. Diphenylnitrosoamine is thus obtained as very pale yellow crystals, m.p. 67 68° yield, 0 9-1 o g. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

Sulphapyridine. Dissolve 18-8 g. of 2-aminopyridine in 40 ml. of dry pyridine (Section 11,47,22) in a 250 ml. flask and add 48 0 g. of p-acetamidobenzenesulphonyl chloride (4) the temperature rises to about 70°. Cool, add excess of water, filter the precipitated 2-(p-acet-amidobenzonesulphonamido)p3Tidine (s acetyl-sulphapyridine) at the pump and recrystallise it from 50 per cent, acetic acid. The yield of pm product, m.py. 224°, is 46-5 g. 

To a mixture of 65 ml of dry benzene and 0.10 mol of freshly distilled NN-di-ethylamino-l-propyne were added 3 drops of BFa.ether and 0.12 mol of dry propargyl alcohol was added to the reddish solution in 5 min. The temperature rose in 5-10 min to about 45°C, remained at this level for about 10 min and then began to drop. The mixture was warmed to 60°C, whereupon the exothermic reaction made the temperature rise in a few minutes to B5 c. This level was maintained by occasional cooling. After the exothermic reaction (3,3-sigmatropic rearrangement) had subsided, the mixture was heated for an additional 10 min at 80°C and the benzene was then removed in a water-pump vacuum. The red residue was practically pure acid amide... 

Gas leaving the economizer flows to a packed tower where SO is absorbed. Most plants do not produce oleum and need only one tower. Concentrated sulfuric acid circulates in the tower and cools the gas to about the acid inlet temperature. The typical acid inlet temperature for 98.5% sulfuric acid absorption towers is 70—80°C. The 98.5% sulfuric acid exits the absorption tower at 100—125°C, depending on acid circulation rate. Acid temperature rise within the tower comes from the heat of hydration of sulfur trioxide and sensible heat of the process gas. The hot product acid leaving the tower is cooled in heat exchangers before being recirculated or pumped into storage tanks. 

The kieis aie of varying sizes and production units can handle from 225—1400 kg, adjusting proportionally the pump size and speed. Most machines are highly versatile so as to accommodate the kind of textile being dyed they are able to control rate of temperature rise, volume ofHquor flow, and time of dye apphcation. 

In a submerged-tube FC evaporator, all heat is imparted as sensible heat, resulting in a temperature rise of the circulating hquor that reduces the overall temperature difference available for heat transfer. Temperature rise, tube proportions, tube velocity, and head requirements on the circulating pump all influence the selec tion of circulation rate. Head requirements are frequently difficult to estimate since they consist not only of the usual friction, entrance and contraction, and elevation losses when the return to the flash chamber is above the liquid level but also of increased friction losses due to flashing in the return line and vortex losses in the flash chamber. Circulation is sometimes limited by vapor in the pump suction hne. This may be drawn in as a result of inadequate vapor-liquid separation or may come from vortices near the pump suction connection to the body or may be formed in the line itself by short circuiting from heater outlet to pump inlet of liquor that has not flashed completely to equilibrium at the pressure in the vapor head. 

The Hvp, vapor head, is calculated by ob.serving the fluid temperature, and then consulting the water properties graph in this chapter. Let s say we re pumping water at 50° F (10° C). The Hvp is 0.411 feet. If the water is 212° F (100° C) then the Hvp is 35.35 feet. The vapor head is subtracted because it robs energy from the fluid in the suction pipe. Remember that as the temperature rises, more energy is being robbed from the fluid. Next, we mu.st subtract the Hf... 

The tests are performed in a special overspeed chamber, which is evacuated to a minimum level to minimize windage pumping of the impeller and to control the temperature rise in the impeller. 

If heat ean be removed as fast as it is generated by the reaetion, the reaetion ean be kept under eontrol. Under steady state operating eonditions, the heat transfer rate will equal the generation rate (see Figure 6-26). If the heat removal rate Qj. is less than the heat generation rate Qg (e.g., a eondition that may oeeur beeause of a eooling water pump failure), a temperature rise in the reaetor is experieneed. The net rate of heating of the reaetor eontent is the differenee between Equations 12-44 and 12-45. 

The acid-rich potassium carbonate solution from the bottom of the absorber is flashed to a flash drum, where much of the acid gas is removed. The solution then proceeds to the stripping column, which operates at approximately 245 °F and near-atmospheric pressure. The low pressure, combined with a small amount of heat input, drives off the remaining acid gases. The lean potassium carbonate from the stripper is pumped back to the absorber. The lean solution may or may not be cooled slightly before entering the absorber. The heat of reaction from the absorption of the acid gases causes a slight temperature rise in the absorber. 

In the summer, the COP of an air-to-air heat pump decreases as the outdoor temperature rises, reducing the cooling capacity. Normally the thermal needs of the building are met since it is common practice to size a heat pump so that it will deliver adequate cooling capacity in all but the most extreme summer conditions. The winter heating capacity of the system is then determined by this tradeoff, and if the heating capacity is inadequate, supplemental electric or fossil fuel heat is required. 

Temperature rise in average pump during operation... 

ATr = temperature rise, °F/min Pso brake horsepower at shutoff or no flow Wi = weight of liquid in pump, Ib.s Cp = specific heat of liquid in pump... 

Figure 3-59. Typical temperature rise for boiler feed water pump. (By permission, Transamerica Delaval Engineering Handbook, 4th ed., H. J. Welch, ed., 1983, Transamerica Delaval, Inc., IMO Industries, Inc., Div.)...

Figure 3-60. Temperature rise in centrifugal pumps in terms of total head and pump efficiency. (By permission, Karassik, I. and Carter, R., Centrifugai Pumps, McGraw-Hill Book Co. Inc., 1960, p. 438.)...

Using the example of Reference [6], assume a pump with characteristic curve and added temperature rise data as showm on Figure 3-59 is to handle boiler feed water at 220°F, with a system available NPSH = 18.8 feet. The v apor pressure of w ater at 220°F is 17.19 psia from steam tables and the SpGr = 0.957. Correcting the 18.8 feet NPSHa psia = 18.8 (l/[2.31/0.957)] = 7.79 psia at 220°F. 

A plotted curve as shown on Figure 3-59 [33] show s that at point A a rise of 20°F on the temperature rise curve corresponds to a flow of 47 GPM minimum safe for the pump handling 220°F, with NPSH of 18.8 feet. 

At = Temperature rise, °F AT,. = Temperature rise, °F/rain t = Piston speed or travel, ft/min V = Liquid velocity, ft/sec v = Average velociry, ft/sec W = Width of channel vtith series pump, ft Wj = Weight of liquid in pump, lb whp = Water or liquid horsepower... 

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