Heat exchanger orifices

A regulator is a compact device that maintains the process variable at a specific value in spite of disturbances in load flow. It combines the functions of the measurement sensor, controher, and final control element into one self-contained device. Regulators are available to control pressure, differential pressure, temperature, flow, hquid level, and other basic process variables. They are used to control the differential across a filter press, heat exchanger, or orifice plate. Regulators are used for monitoring pressure variables for redundancy, flow check, and liquid surge relief. 

The discharge pressure developed hy the compressor must he equal to the process gas s total system resistance, of control valves, hand valves, orifices, heat exchangers, and any other process-related devices through which the discharge gas from the compressor must flow. As this resistance changes, the gas flow through the compressor will automatically adjust itself to equal the new resistance. ... 

A liquid hydrocarbon is fed at 295 K to a heat exchanger consisting of a 25 mm diameter tube heated on the outside by condensing steam at atmospheric pressure. The flow rate of the hydrocarbon is measured by means of a 19 mm orifice fitted to the 25 nnn feed pipe. The reading on a differential manometer containing the hydrocarbon-over-water is 450 mm and the coefficient of discharge of the meter is 0.6. 

Operating line, humidifying towers 778 Optimum pipe diameter, example 371 — water velocity, heat exchanger 505 Orifice meter 244,246, 248... 

Control valve pressure drop, allow normal (xl.22) maximum Heat exchanger, allow normal (xl.22) maximum Orifice, allow normal (xl.22) maximum... 

The main components of the GM-type PTR are shown in Fig. 5.21(b). From the left to the right, the pulse tube system consists of a compressor (CP), a room temperature heat exchanger or an after-cooler (E,), a rotary valve (RV), a regenerator (RG), a low-temperature heat exchanger (Ej), a pulse tube (PT), another room temperature heat exchanger (E3), two orifices (C and 02) and a buffer volume (BF). 

Step 1. From a to b and c. When the pressure rises, the gas element moves through the regenerator in the direction of the heat exchanger E2 (from a to b). According to the assumptions, the heat exchange is perfect, and the temperature of the gas element is equal to the temperature of the regenerator. At point b, the gas element leaves E2 and enters the tube with the temperature Th. From b to c, the gas element is compressed adiabatically, while it moves towards the orifice. Its temperature rises together with the pressure. 

Step 4. From e to f and a. The expansion stops, and the orifice is open again. The gas continues to flow in the direction of E2. From e to f the pressure is constant, so the temperature is constant as well. At point f, the gas parcel enters E2 with T < Tl. When passing E2, the gas warms up to the temperature Th. The amount of heat, which the gas takes away from the heat exchanger, is the cooling power. In the remaining time of the cycle, the gas element moves inside the regenerator to its original position. 

For some products it has been found advantageous to pressurise the plate heat exchanger, with an orifice or valve preventing boiling until the liquor enters the separator, in what is known as the APV Paraflash system. This is a special case of the forced circulation evaporator described earlier. 

The temperature transmitter on the process oil stream leaving the heat exchanger has a range of 5 -150°F. The range of the orifice-differential pressure flow transmitter on the chilled water is O-ISOO gpm. Alt instrumentation is electronic (4 to 20 mAV Assume the chilled-water pump is centrifugal with a flat pump curve. 

The pump suction pressure is constant at 10 psig. The design flow rate is 500 gpm. At this flow rate the pressure drop over the flow orifice is 2 psi, through the piping is 30 psi, over three heat exchangers is 32 psi, and over the furnace is 60 psi. Assume a flat pump curve and a specific gravity of 1. 

Figure 12.13. Types of baffle used in shell and tube heat exchangers, (a) Segmental, (b) Segmental and strip, (c) Disc and doughnut, (d) Orifice.

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