150 120

FIG. 11-116 Propane precooled mixed-refrigerant cycle cooling curve for natural gas. Mixed refrigerant V (Stage 1) FIG. 11-116 Propane precooled mixed-refrigerant cycle cooling curve for natural gas. coolers are generally classified as regenerative or recuperative. Regenerative coolers use reciprocating components that move the working fluid back and forth through a regenerator. The recuperative coolers, on the other hand, use countercurrent heat exchangers to accomplish the heat transfer...

Refrigeration

Basic Basic Refrigeration Mechanical Refrigeration (Vapor-Compression Systems) 11-77 Vapor-Compression Multistage Cascade Positive-Displacement Centrifugal System System, Equipment, and Refrigerant Other Refrigerant Systems Applied in the Industry Absorption Refrigeration Steam-Jet (Ejector) Multistage Capacity Secondary Refrigerants (Antifreezes or Organic Compounds (Inhibited Safety in Refrigeration

00047

To convert British thermal units per hour-square foot-degrees Fahrenheit to joules per meter-second-kelvins, multiply by 1.7307 to convert British thermal units per cubic foot-degrees Fahrenheit to joules per cubic meter-kelvins, multiply by (6.707)(104) and to convert square feet per hour to square meters per second, multiply by (2.581)(10-5). To convert British thermal units per hour-square foot-degrees Fahrenheit to joules per meter-second-kelvins, multiply by 1.7307 to convert British...

Info

0 Refrigeration capacity kW 100 FIG. 11-84 Typical power-refrigeration capacity data for different types of compressors during partial, unloaded operation. backwards into the compressor, causing losses shown in Fig. 11-85b and the last stage will be only discharge without compression. The case when the compressor discharge pressure is equal to the condensing pressure is shown in the Fig. 11-85c. Double helical rotary (twin) screw compressors consist of two mating helically grooved rotors (male...

Economic Thickness Of Insulation

Optimal economic insulation thickness may be determined by various methods. Two of these are the minimum-total-cost method and the incremental-cost method (or marginal-cost method). The minimum-total-cost method involves the actual calculations of lost energy and insulation costs for each insulation thickness. The thickness producing the lowest total cost is the optimal economic solution. The optimum thickness is determined to be the point where the last dollar invested in insulation results in...

Pvdf Heat Exchangers

These shell-and-tube-type exchangers are similar to the Teflon designs but have some mechanical advantages over Teflon units. First the tubes are available in 9.5 mm sizes which reduces the chances of plugging that are found in Teflon units with unfiltered fluids. Second, the material has higher strength even at lower temperatures almost double. Larger units are possible with PVDF materials. Tube to tubesheet joints, a weakness of most nonmetallic units, are fused by special techniques that do...

Shellandtube Exchanger Costs

Basic costs of shell-and-tube heat exchangers made in the United States of carbon steel construction in 1958 are shown in Fig. 11-41. 3 4 x 16' tubes, la pitch 3 4 x 16' tubes, 15 16A pitch 3 4 x 20' tubes, lo pitch 3 4 x 20' tubes, 15 16 a pitch I x 16' tubes, I 1 4 pitch, below 1000 sq. ft. lx 16' tubes, I 1 4 O pitch, 1000 sa. ft. and above l x 16' tubes, I 1 4 a pitch, below 1000 sq. ft. I x 16' tubes, I 1 4 a pitch, 1000 sq. ft. and above lx 16' tubes, I 1 4 a pitch l x 16' tubes, 11 4 a...

100 150 200 250 300

FIG. 11-18 Acceleration losses in boiling flow. C ( F - 32) 1.8. 100 150 200 250 300 Vapor temperature, F. FIG. 11-19 Friction pressure drop in boiling flow. C ( F - 32) 1.8. 100 150 200 250 300 Vapor temperature, F. FIG. 11-19 Friction pressure drop in boiling flow. C ( F - 32) 1.8. where b (2.6)(107)(SI) and 1.0 (U.S. customary) and using r2 from Fig. 11-18. The frictional pressure drop is derived from Fig. 11-19, which shows the ratio of two-phase pressure drop to that of the entering liquid...

Insulation Materials

Materials Thermal insulations are produced from many materials or combinations of materials in various forms, sizes, shapes, and thickness. The most commonly available materials fall within the following categories Fibrous or cellular mineral. Alumina, asbestos, glass, perlite, rock, silica, slag, or vermiculite. Fibrous or cellular organic. Cane, cotton, wood, and wood bark (cork). Cellular organic plastics. Elastomer, polystyrene, polyisocyanate, polyisocyanurate, and polyvinyl acetate....

Cryogenic Instrumentation

Even though the combined production of cryogenic nitrogen and oxygen exceeds the production of any other chemical in the United States, the cryogenic industry does not appear to warrant a separate product line of instruments for diagnostic and control purposes. Low-temperature thermometry is the one exception. The general approach generally is that instruments developed for the usual CPI needs must be modified or accepted as is for cryogenic use. Quite often problems arise when instruments for...

Heattransfer Equipment For Sheeted Solids

Cylinder Heat-Transfer Units Sometimes called can dryers or drying rolls, these devices are differentiated from drum dryers in that they are used for solids in flexible continuous-sheet form, whereas drum dryers are used for liquid or paste forms. The construction of the individual cylinders, or drums, is similar in most respects to that of drum dryers. Special designs are used to obtain uniform distribution of steam within large drums when uniform heating across the drum surface is critical. A...

General Design Considerations

Selection of Flow Path In selecting the flow path for two fluids through an exchanger, several general approaches are used. The tubeside fluid is more corrosive or dirtier or at a higher pressure. The shell-side fluid is a liquid of high viscosity or a gas. When alloy construction for one of the two fluids is required, a carbon steel shell combined with alloy tube-side parts is less expensive than alloy in contact with the shell-side fluid combined with carbon steel headers. Cleaning of the...

Other Refrigeration Systems Applied In The Industry

Absorption Refrigeration Systems Two main absorption systems are used in industrial application lithium bromide-water and ammonia-water. Lithium bromide-water systems are limited to evaporation temperatures above freezing because water is used as the refrigerant, while the refrigerant in an ammonia-water system is ammonia and consequently it can be applied for the lower-temperature requirements. Single-effect indirect-fired lithium bromide cycle is shown in Fig. 11-99. The machine consists of...

Thermal Design Of Reboilers

For a single-component reboiler design, attention is focused upon the mechanism ofheat and momentum transfer at the hot surface. In multicomponent systems, the light components are preferentially vaporized at the surface, and the process becomes limited by their rate of diffusion. The net effect is to decrease the effective temperature difference between the hot surface and the bulk of the boiling liquid. If one attempts to vaporize too high a fraction of the feed liquid to the reboiler, the...

6776

One interesting consequence of this fact is the inability to construct a hairpin tube bundle having the smallest radius bends common to a conventional U-tube, TEMA shell, and tube bundle. In fact, in the larger hairpin sizes the tubes might be better described as curved rather than bent. The smallest U-bend diameters are greater than the outside diameter of shells less than 300 mm in size. The U-bend diameters are greater than 300 mm in larger shells. As a general rule, mechanical tube cleaning...

15

Base Bare-tube external surface 1 in. o.d. by 12 B.W.G. by 24 ft. 0 in. steel tube with 8 aluminum fins per inch V-in. high. Steel headers. 150 lb. sq. in. design pressure. V-belt drive and explosion-proof motor. Bare-tube surface 0.262 sq. ft. ft. Fin-tube surface bare-tube surface ratio is 16.9. Factors 20 ft. tube length 1.05 18 B.W.G. admiralty tube 1.04 16 B.W.G. admiralty tube 1.12 NOTE To convert feet to meters, multiply by 0.3048 to convert square feet to square meters, multiply by...

Heattransfer Equipment For Divided Solids

Most equipment for this service is some adaptation of a material-handling device whether or not the transport ability is desired. The old vertical tube and the vertical shell (fluidizer) are exceptions. Material-handling problems, plant transport needs, power, and maintenance are prime considerations in equipment selection and frequently overshadow heat-transfer and capital-cost considerations. Material handling is generally the most important aspect. Material-handling characteristics of the...

Liquid Suction Vapour Heat Exchanger

Ammonia Refrigeration System Diagram

For the heat pump (HP) operation, heat rejected at the high temperature (Qhigh) is the objective, thus COPHP 2 + W COPR + 1 (11-85) For a Carnot cycle (where AQ TA s), the COP for the refrigeration application becomes (note than T is absolute temperature K ) The COP in real refrigeration cycles is always less than for the ideal (Carnot) cycle and there is constant effort to achieve this ideal value. Basic Refrigeration Methods Three basic methods of refrigeration (mentioned above) use similar...

Baffles And Tube Bundles

Tie Rod And Spacer Heat Exchanger

The tube bundle is the most important part of a tubular heat exchanger. The tubes generally constitute the most expensive component of the exchanger and are the one most likely to corrode. Tube sheets, baffles, or support plates, tie rods, and usually spacers complete the bundle. Minimum baffle spacing is generally one-fifth of the shell diameter and not less than 50.8 mm (2 in). Maximum baffle spacing is limited by the requirement to provide adequate support for the tubes. The maximum...

Thermal Design For Solids Processing

Solids in divided form, such as powders, pellets, and lumps, are heated and or cooled in chemical processing for a variety of objectives such as solidification or fusing (Sec. 11), drying and water removal (Sec. 20), solvent recovery (Secs. 13 and 20), sublimation (Sec. 17), chemical reactions (Sec. 20), and oxidation. For process and mechanical-design considerations, see the referenced sections. Thermal design concerns itself with sizing the equipment to effect the heat transfer necessary to...

Equipment

Reciprocating Compressor Curve

Compressors These could be classified by one criteria (the way the increase in pressure is obtained) as positive-displacement and FIG. 11-79 Pressure enthalpy diagram for typical two-stage system with two evaporating temperatures, flash-gas removal, and intercooling. FIG. 11-79 Pressure enthalpy diagram for typical two-stage system with two evaporating temperatures, flash-gas removal, and intercooling. dynamic types as shown in Fig. 11-81 (see Sec. 10 for drawings and mechanical description of...

Brazedplatefin Heat Exchanger

Brazed-aluminum-plate-fin heat exchangers (or core exchangers or cold boxes) as they are sometimes called, were first manufactured for the aircraft industry during World War II. In 1950, the first tonnage air-separation plant with these compact, lightweight, reversing heat exchangers began producing oxygen for a steel mill. Aluminum-plate-fin exchangers are used in the process and gas-separation industries, particularly for services below -45 C. Core exchangers are made up of a stack of...

Fouling And Scaling

Fouling refers to any change in the solid boundary separating two heat transfer fluids, whether by dirt accumulation or other means, which results in a decrease in the rate of heat transfer occurring across that boundary. Fouling may be classified by mechanism into six basic categories 1. Corrosion fouling. The heat transfer surface reacts chemically with elements of the fluid stream producing a less conductive, corrosion layer on all or part of the surface. 2. Biofouling. Organisms present in...

Equipment For Solidification

A frequent operation in the chemical field is the removal of heat from a material in a molten state to effect its conversion to the solid state. When the operation is carried on batchwise, it is termed casting, but when done continuously, it is termed flaking. Because of rapid heat transfer and temperature variations, jacketed types are limited to an initial melt temperature of 232 C (450 F). Higher temperatures to 316 C (600 F) require extreme care in jacket design and cooling-liquid flow...

Aircooled Heat Exchangers

Forced Draft Air Coolers Working

Atmospheric air has been used for many years to cool and condense fluids in areas of water scarcity. During the 1960s the use of air-cooled heat exchangers grew rapidly in the United States and elsewhere. In Europe, where seasonal variations in ambient temperatures are relatively small, air-cooled exchangers are used for the greater part of process cooling. In some new plants all cooling is done with air. Increased use of air-cooled heat exchangers has resulted from lack of available water,...

Evaporator Types And Applications

Types Calandria

Evaporators may be classified as follows 1. Heating medium separated from evaporating liquid by tubular heating surfaces. 2. Heating medium confined by coils, jackets, double walls, flat plates, etc. 3. Heating medium brought into direct contact with evaporating liquid. By far the largest number of industrial evaporators employ tubular heating surfaces. Circulation of liquid past the heating surface may be induced by boiling or by mechanical means. In the latter case, boiling may or may not...

Thermal Design Of Evaporators

Engineering Design Handbook

Heat duties of evaporator heating surfaces are usually determined by conventional heat and material balance calculations. Heating surface areas are normally, but not always taken as those in contact with the material being evaporated. It is the heat transfer A T that presents the most difficulty in deriving or applying heat-transfer coefficients. The total A T between heat source and heat sink is never all available for heat transfer. Since energy usually is carried to and from an evaporator...

Thermal Design Of Condensers

Mean Temperature Difference In condensing a single component at its saturation temperature, the entire resistance to heat transfer on the condensing side is generally assumed to be in the layer of condensate. A mean condensing coefficient is calculated from the appropriate correlation and combined with the other resistances in Eq. 11-2 . The overall coefficient is then used with the LMTD no FT correction is necessary for isothermal condensation to give the required area, even though the...

Engineer Steel 2972

Eng. Chem., 36, 510 1944 give film coefficients for heating and cooling agitated fluids using a coil in a jacketed vessel. Because of the many factors affecting heat transfer, such as viscosity, temperature difference, and coil size, the values in this table should be used primarily for preliminary design estimates and checking calculated coefficients. C F - 32 1.8 to convert British thermal units per hour-square foot-degrees Fahrenheit to joules per square...

114

FIG. 11-1 Temperature profiles in heat exchangers. a Countercurrent. b Cocurrent. UomATm to use in Eq. 11-4 is Colburn, Ind. Eng. Chem., 25, 873 1933 U t'i -f - U'M -f for countercurrent flow, where U is the overall coefficient evaluated when the stream temperatures are t1 and t and U' is evaluated at t'2 and t. The corresponding equation for cocurrent flow is U fi - f - U0 f2 - f where U' is evaluated at t2 and t and Uo is evaluated at t1 and t. To use these equations, it is necessary to...