MODUL 5 Perancangan Alat Pengubah Panas, Tekanan dan Fasa

MODUL 5

Perancangan Alat Pengubah Panas, Tekanan dan Fasa

Donna Imelda, S.T., M. Si dan Ir. Lubena, M.T.

Chemical Engineering Department

JayabayaUniversity

RPKPS

KOMPETENSI

MEMAHAMI JENIS-JENIS PERALATAN TERKAIT DENGAN

PERUBAHAN YANG TERJADI PADA TEMPERATURE, TEKANAN

DAN FASA

INDIKATOR

MAHASISWA MAMPU MEMILIH ALAT YANG TEPAT YANG DIPERLUKAN DALAM PROSES

UNTUK MENGUBAH PANAS, TEKANAN DAN FASA

MATERI

ALAT PENGUBAH PANAS, TEKANAN DAN FAS SEPERTI: HE, KOMPRESOR, KONDENSOR DLL.

Alat Pengubah

Panas

Basic Concept



Heat is transferred to or from process streams using other process streams or heat-transfer media.

 In a final process design, every effort is made to exchange heat between process streams and thereby minimize the use of heat-transfer media

 Inevitably, however, some use of media, mostly cooling water, steam, and the products of combustion, is necessary.

 Heat-transfer media are classified as coolants (heat sinks) when heat is

transferred to them from process streams, and as heat sources when heat is

transferred from them to process streams

Heat Transfer Media

 Process design includes the selection of appropriate heat-transfer media, data for which are listed in Table 18.1, where the media are ordered by temperature range of application.

 The most common coolant, by far, is cooling water, which is circulated through a cooling tower.

 The cooling tower restores the cooling water temperature by contacting the water with air, causing evaporation of a small amount of the water.

Heat Transfer Media

 The most common heat source for heating and/or vaporizing process streams in autility exchanger is steam, which is available in most chemical plants from a boiler, at two, three, or more pressure levels

 When exchanger inlet temperatures of

process streams to be cooled are higher than 250 F, consideration is given to transferring at least some of the heat to treated boiler feed water to produce steam.

EQUIPMENT FOR HEAT EXCHANGE

 As listed in Table 18.2, a wide variety of equipment is available for conducting heat exchange.

 Commercial units range in size from very small, double-pipe heat exchangers, with less than 1 ft2 of heat-transfer surface, to large, air cooled units called fin-fan heat exchangers because they consist of tubes with external peripheral fins and fans to force air past the tubes.

 For specialized applications, compact heat exchangers are challenging shell-and-tube units.

Double-Pipe Heat Exchangers

 A typical double-pipe unit is shown in Figure. In its simplest

form, it consists of an inner straight pipe of circular cross section,

concentric to and supported within an outer straight pipe by means of packing glands.

 One stream flows through the inner pipe, while the other stream flows counter currently through the annular passage between the outer wall of the inner pipe and the inner wall of the outer pipe.

Double-Pipe Heat Exchangers

Fin-Fan Heat Exchangers

Fin-Fan Heat Exchangers

Heat-transfer area per unit volume is greatly increased by placing a large number of small-diameter tubes inside a shell, that is, a pressure vessel.

Shell-and-tube heat exchangers, whose design is standardized by the Tubular Exchanger Manufacturers Association (TEMA) and has

changed little in almost 70 years

Shell-and-Tube

Heat Exchangers

HEAT EXCHANGEr SHELL AND TUBE

HEAT EXCHANGEr SHELL AND TUBE

Cooling Tower

Alat

Pengubah Tekanan

 Movement of gases can be accomplished by use of fans, blowers, vacuum pumps, and compressors.

 Fans are useful for moving gases when pressure differences less than about 0.5 psi are involved.

 Centrifugal blowers can handle large volumes of gases, but the delivery pressure is limited to approximately 50 psig.

 Reciprocating compressors can be employed over a wide range of capacities and pressures, and they are used

extensively in industrial operations.

 Sizes of reciprocating compressors ranging from less than 1 to 3000 hp are available, and some types can give delivery pressures as high as 4000 atm.

Pressure Machine

 Fans accept gases at near atmospheric pressure and raise the pressure by approximately 3% (12 in. of water), usually on air for ventilating or circulating purposes.

 Blowers is a term applied to machines that raise the pressure to an intermediate level, usually to less than 40 psig, but more than accomplished by fans.

 Compressors are any machines that raise the pressure above the levels for which fans are used.

Thus, in modern terminology they include blowers.

 Jet compressors utilize a high pressure gas to raise other gases at low pressure to some intermediate value by mixing with them.

 Vacuum pumps produce subatmospheric pressures in process equipment. Often they are compressors operating in reverse but other devices also are employed.

 Steam jet ejectors are used primarily to evacuate equipment but also as pumps or compressors.

Alat Pengubah Tekanan

 Movement of gases can be accomplished by use of fans, blowers, vacuum pumps, and compressors.

 Fans are useful for moving gases when pressure differences less than about 0.5 psi are involved.

 Centrifugal blowers can handle large volumes of gases, but the delivery pressure is limited to approximately 50 psig.

 Reciprocating compressors can be employed over a wide range of capacities and pressures, and they are used

extensively in industrial operations.

 Sizes of reciprocating compressors ranging from less than 1 to 3000 hp are available, and some types can give delivery pressures as high as 4000 atm.

Kompresor

 Compressor efficiencies are usually expressed as isentropic efficiencies, i.e., on the basis of an adiabatic reversible process. In either case, the efficiency is defined as the ratio of the power required for the ideal process to the power actually consumed.

 Because the energy necessary for an isentropic compression is greater than that required for an equivalent isothermal compression, the isentropic efficiency is always greater than the

isothermal efficiency.

 For reciprocating compressors, isentropic efficiencies are generally in the range of 70 to 90 percent and isothermal efficiencies are about 50 to 70 percent.

 Multistage compression is necessary for high efficiency in most large compressors if the ratio of the delivery pressure to the intake pressure exceeds approximately 5 : 1.

Alat Pengubah

Fasa

Solid to Liquid - Melter

Freeze Drying

Evaporator( Alat Pemekat)

VAPORIZER

Vaporizer Adalah alat yang digunakan untuk mengubah fase cair menjadi fase uap.

CARA KERJA VAPORIZER

Pada suhu tertentu, moleku dari zat volatile dalam tempat tertutup akan

berdistribusi dalam fase cair dan gas. Molekul gas akan menghantam dinding

container, menciptakan tekanan uap dari zat itu, makin tinggi suhu yang

dihasilkan makan makin tinggi kecenderungan molekul yang berubah daric

air ke gas, dan makin tinggi tekanan uapnya. Penguapan memerlukan energi,

yang didapat dari kehilangan panas dari fase cair. Ketika penguapan

berlangsung, temperature zat cair turun dan tekanan uap menurn hingga

terdapat kalor yang dapat masuk ke sistem. Vaporizer memiliki ruangan

dimana gas pembawa akan larut bersama zat volatil.

JENIS-JENIS VAPORIZER 1. Fluotec vaporizer

Jenis vaporizer yang keakuratannya dipengaruhi oleh suhu, lamanya

penggunaan, jumlah halothane yang berefek didalamnya, dan aliran gas yang diberikan.

2. Vaporizer copper kettle

Vaporizer jenis ini digunakan sebagai alat pengukur atas berbagai aliran gas oksigen yang diberikan melewati cairan halotan dan hasil campuran uap yang dikeluarkan dan dapat diketahui hasil penukurannya.

3. Drager vaporizer

Vaporizer dengan kompensasi suhu yang dapat mengeluarkan konsentrasi yang tepat dan akurat pada aliran gas. Alat ini tidak terpengaruh oleh

tekananyang ditimbulakan oleh ventilator.

Gambar : VAPORIZER Natural Gas

VAPORIZER

Vaporizers for Liquid Carbon Dioxide

Gambar : Water circulation vaporizers

Evaporator( Alat Pemekat)

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