sample problems in industrial plant design

8/3/2019 Sample Problems in Industrial Plant Design

1/26

Sample Problems in Industrial Plant Design

Pumps

Problem No. 1

Determine the specific speed of a centrifugal pump delivering 7500 gpm acting

against a total head of 370 feet and operating at 1000 rpm.

Given:

Q = 7500 gpmH = 370 ftN = 1000 rpm

Find:Ns = ?

Solution:

Problem No. 2

Pumps A and B belong to the same family and are operating at homologous points.

For Pump A For Pump B

D = 2 feet D = 3 feetN = 1000 rpm Q = 6500 gpmAt its best efficiency point (BEP)H = 200 feet

Q = 8000 gpm

How fast should pump B run if it s to operate as its best efficiency point?


2/26

Solution:By Pumps Similarity Laws

Problem No. 3

A centrifugal pump is used to deliver 500 000 li/hr of water from a reservoir located5 meters below the pump to a pressure tank whose pressure is 3 kg/cm2. It is alsoestimated that friction losses in the 250-mm suction and 175-mm discharge pipe are 3m and 1.5 m, respectively. Assuming a pup efficiency of 68%, calculate for the nominal

rating of the motor in kW.

Given:Q = 500 000 li/hr

H = 5 mP2 = 3 kg/cm

2 = 294.1995 KPaDs = 250 mmhfs = 3 mDd = 175 mmhfd = 1.5 mpump = 68%

Find:

Pbrake = ?

Solution:

(

)


3/26

Then:

( )

Problem No. 4

A mixed-flow pump operating at 500 rpm and delivering 60m3/min has a specificspeed of 100 rpm. The suction flange is 600 mm in diameter and has an absolutepressure of 50 kPA. The discharge flange is 520 mm in diameter and its centerline is

40cm above the suction centerline. Account for the expected discharged pressure.

Solution:

Where:


4/26

Where:

Problem No. 5

A boiler feed pump receives 300 liters of water at 90C (h = 839.33 kJ/kg) perminute. It is operating against a total head of 800 m. calculate for the enthalpy of the

fluid leaving the pump, in kJ/kg. Assume a pump efficiency of 70 per cent.

Solution:


5/26

Compressor

Problem No. 1

A rotary compressor takes in 360 kg/hr of air at 1 bar, 20C and compresses it to600 kPa with an isentropic compressor efficiency of 75 per cent. Find the power

required to drive the compressor in kW.

Given:m = 360kg/hrP1 = 1 bar = 100KPa

T1 = 20oC = 293K

P2 = 600 KPan = 1.4

compressor = 75%

Find:Pbrake = ?

Solution:

()

( ) ( ) ( )


6/26

Problem No. 2

An air compressor with a clearance of 7% handles 0.6 kg/s of air between thepressures of 1 atm and 400 kPa with a poly tropic constant of 1.25. Temperature of the

air at the beginning of compression is 27C. Calculate for the transferred heat duringthe compression process, in kW.

Solution:

()

( )

Where:

( )( )

Problem No. 3

A two stage reciprocating air compressor is required to deliver 0.9 kg/s of air from 1bar and 27C to 10 bars. The compressor operates at 300 rpm, compression andexpansion processes follow Pv1.33 = constant, and both cylinders have 4.25 per cent

clearance. There is a 10-kPa pressure drop in the intercooler. The low-pressure cylinderdischarges at the optimum pressure into the intercooler. Air enters the high-pressurecylinder at 30C. Intercooler is water-cooled, with the water entering at 290 K andleaving at 300 K. Assuming a 100% heat transfer efficiency, determine the amount ofcooling water required by the intercooler, in li/min.


7/26

Given:m = 0.9 kg/sP1 = 1 bar

T1 = 27 oCP2 = 10 barn = 1.33c = 0.0425

Find:

Vwater = ?

Solution:

()

( )

Problem No. 4A compressor receives air from the surroundings at 1 bar, 27C. there is a pressure

drop of 3 kPa through the intake valves and the temperature at the end of the stroke is39C. discharge pressure drop through the discharge valves. Compressor capacity is 12liters and piston displacement of 15 liters with compressor speed of 200 rpm. Assuminga poly tropic constant of 1.25, account for the probable volumetric efficiency.


8/26

Given:P1 = 1 bar = 100 KPaT1 = 27

oC= 300 KP2 = 97 KPaT2 = 39

oC = 312 K

VC = 12 LVD = 15 LN = 200 rpmn = 1.25

Find:

Ev = ?

Solution:

() ( )

Problem No. 5

A single acting air compressor operated at 375 rpm with an initial condition of 98kPa 21C and discharges the air at 400 kPa. Bore and stroke are 350 mm and 400 mm,respectively. Determine the free air capacity in m3/s/ assume 5% clearance and poly

tropic exponent of 1.25.

Given:N = 375 rpm = 6.25 rev/secP1 = 98 KPaT1 = 21

oC

P2 = 400 KPaD = 350 mmL = 400 mmc = 0.05n = 1.25


9/26

Find:Free air capacity, Vair

Solution:

() ( )

( ) [ ]


10/26

Machine Foundation

Problem No. 1

Given the following data:

10 in x 12 in engine area

4 100-kg engine

SABP of location = 6000 kg/m3

Bedplate dimensions = 5 cm x 2.5 m

Design limit for foundation depth = 0.8 m

Requirement:

Design a rectangular block foundation that is safe against direct settlement.

Express your answer in terms of L x W x H.

Solution:

Allowing 1 foot (0.3m) clearance each side

L = 5m + 2(0.3m) = 5.6m

W = 2.5m + 2(0.3m) = 3.1m

Since the design limit for foundation depth = 0.8m

Therefore:

L = 5.6 m; W = 3.1 m; H = 0.8 m

Problem No. 2

Determine the amount of sand in m3 required for a 5 m3 of 1:2:4 concrete mixture

(refer to Construction Estimate by Max Fajardo), given the following properties:


11/26


12/26

Heat Exchanger

Problem No. 1

One side of a plane wall is maintained at 100C, while the other side is exposed to aconvection environment having T = 10C and h = 10 W/m2- C. The wall has a thermalconductivity k = 1.6 W/m2- C and is 40 cm thick. Calculate for the heat flux through

the wall in W/m2.

Given:T1 = 100

oCT2 = 10

oCh1 = 10 W/m

2-oC

x = 40 cm = 0.4 mk = 1.6 W/m-oC

Find:

Q/A = ?

Solution:


13/26

Problem No. 2

Hot water enters a counter flow heat exchanger at 99C. it is used to heat a coldsteam of water from 4 to 32 C. The flow rate of the cold stream is 1.3 kg/s, and the

flow rate of the hot stream is 2.6 kg/s. the overall heat transfer coefficient is 830 W/m 2- C. Compute for the heat exchange area in m2.

Given:Hot water Cold waterTh1 = 99

oC Tc1 = 4oC

mh = 2.6 kg/s mc = 1.3 kg/s

U = 830 W/m2-oC

Find:

A = ?

Solution:


14/26

Problem No. 3

A two-meter steel pipe with a 5-cm outer diameter is covered with a 6.4-mm layerof asbestos insulation, k = 0.096Btu/hr-ft-oF, followed by a 2.5-cm layer of fiberglass

insulation, k = 0.028 Btu/hr-ft-oF. The pipe wall temperature is 315oC and the outsideinsulation temperature is 38oC. Determine the heat transfer in watts.

Solution:


15/26

Transformer

Problem No. 1

The secondary of a 20 Kva, 60-cycle transformer has 120 turns and the flux in thecore has a maximum value of 720,000 maxwells. If the primary has 1200 turns,

determine the primary voltage in volts.

Given:f = 60cycleN1 = 1200 turns

N2 = 120 turns

Find:Primary voltage, E1

Solution:

( )

( )


16/26

Refrigeration

Problem No. 1

A single stage vapor-compression refrigeration system uses Freon-12 to produce 10tons of refrigeration when operating between a condensing temperature of 40C (960.7KPa) and an evaporating temperature of -10C (219.1 KPa). The specific enthalpy ofsaturated liquid at condenser pressure is 74.527 kJ/kg. The specific enthalpy andspecific volume of saturated vapor at evaporator pressure are 183.058kj/kg, and

0.076646/kg, respectively. Assuming the specific enthalpy of superheated vaporleaving the compressor equal to 209.5 kJ/kg.

Determine the following:a) Compression ratiob) Refrigerating effect, in kJ/kgc) Refrigerant mass flow rate, in kg/sd) Refrigerant volume flow rate, in 3e) Heat rejected in the condenser, kWf) Compressor power, kWg) COP of the systemh) Refrigerating efficiency, i) Degrees superheat, SH

j) Compressor power, in kW, if adiabatic efficiency is 80%

Given:

QA= 10 TOR

T3 = 40C

P2 =P3 =

T4 = 960.7 KPa

P4 = 219.1 KPa

h4 =h3 =74.527 kJ/kg

h1 = 183.058 kJ/kg

v1 = 0.076646 /kgh2 = 209.5 kJ/kg


17/26

Solution:

1.2 RE = h1 - h4

= (183.058 - 74.527) kJ/kg

RE = 108.531 kJ/kg

1.3 m =

m =

m = 0.324 kg/s

1.4 v = = vm

v = (0.324 kg/s) (0.076646 /kg)v = 0.025

1.5 Wc = m (h2 - h1)

Wc = (0.324 kg/s) (209.5-183.058) kJ/kg

Wc = 8.57 KW

1.6 QR = m (h2 h3)

QR = (0.324 kg/s) (209.5-74.527) kJ/kg

QR = 43.73 KW

1.7 COP =

COP = COP = 4.10

1.0 Compressor Power = = = 10.71 KW


18/26

Problem No. 2

A small cold storage plant is used to store 2 metric tons of onions daily. The onionsare available at 37C and the storage temperature is -5C. The specific heats of onionsbefore and after freezing are 3.81kJ/kg-C and 2.13kJ/kg-C, respectively. The freezingtemperature is -1.0C. Latent heat of fusion is 302kJ/kg. Heat of respiration is 4 650kJ/metric ton per 24hours. If the refrigerating machine operates 24 hours a day and thechilling rate factor is 0.80, determine the capacity of the machine required in tons of

refrigeration (TR).

Given:monion =2Mt = 2000kgTonion = 37

oCT

storage= -5oC

Conion = 3.81kJ/kg-oC (before freezing)

= 2.13 kJ/kg-oC (after freezing)Tfreezer = -1.0

oCQL = 302kJ/kgQR= 4650 kJ/Mt per 24 hour

Find:Capacity of machine in TOR = ?

Solution:

[ ] ( ) [ ] [ ] ( )


19/26

Problem No. 3

An ice plant produces 20 tons of ice per day at -15 C from water at 25C. ifmiscellaneous losses are 12 per cent of the chilling and freezing load, calculate for the

refrigeration capacity of the ice plant, in TR.

Solution: * + *

+ (

)

* +


20/26

Air Conditioning

Problem No. 1

Indoor design conditions of a certain theatre require that 26C dry bulb and 50%relative humidity is maintained. Air is to be supplied at 16C where as outside air is at30C dry bulb and 60% relative humidity. Take the sensible heat load and latent heatload as 200 KW and 50 KW, respectively. Assuming ventilating air as 20% of the supply

air, determine the tons of refrigeration required by the conditioner.

Solution:

From psychrometric chart

By mass balance:

Where:

By heat balance:


21/26

Problem No. 2

A cooling tower of a large industrial cold storage plant cools 12,000 kg/s of waterfrom 35C to 25C. The inlet air to the cooling tower has a temperature of 25C dry-bulb and 35% relative humidity. Air leaves the cooling tower saturated at 35C.Calculate for the volume flow rate of air required by the cooling tower in /min if thespecific volume of the inlet air is 0.75 /kg.

Solution:

From psychrometric chart:


22/26

Problem No. 3

Condenser cooling water is supplied to the forced-draft fan at 40C. The coolingtower approach temperature is 3C. Air enters the tower at 25C dry-bulb and 20Cwet-bulb with moisture content of 0.0128 kgv/kgda and specific enthalpy of 57.5 KJ/kgdaand leaves at 38C dry-bulb, 60% relative humidity with moisture content of 0.0256kgv/kgda and specific enthalpy of 104 Kj/kgda. For 5 000 liters per minute of condenserwater entering the cooling tower, determine the amount of make-up water requires in

L/min to compensate for the evaporation losses.

Solution:


23/26

Problem No. 4

A copra-drying plant is designed to dry 1000 kg/hr of fresh coconut 30% water. Theraw copra from the dryer contains 5 % water. Fresh air at 27C and 40% relative

humidity and barometric pressure of 98 kPa has a humidity ratio of 0.0083 kg w/kgda andan enthalpy of 50.86Kj/kgda. The air is heated to 110C (h=135.58kJ/kgda) beforeentering the adiabatic drying chamber ratio of 0.02285kgw/kgda. Assuming 100 percentheat transfer efficiency in the air preheater, find the amount of steam required by thedryer when condensing saturated steam required by the dryer when condensingsaturated steam to saturated liquid at 150kPa (h fg=2226.5kJ/kg). Express answer in

kg/hr.

Solution:

Problem No. 5

Wet feed containing 70% moisture leaves a rotary dryer with a bone with a bone

dry weight of 90%. Determine weight of moisture removed in kg based on:

a) One kilogram of original wet feedb) One kilogram of final dried productc) One kilogram of bone-dry material


24/26

Solution:

a. 1kg of original wet feed

b. 1kg of dried product

c. 1 kg of bone-dry product


25/26

Bataan Peninsula State University (Main Campus)

Balanga City, Bataan

College of Engineering and Architecture

Department of Mechanical Engineering

MEID 512

INDUSTRIAL PLANT DESIGN


26/26

Sample Problems in Industrial Plant Design

Submitted By:

Surname Given Name Middle Initial

Cruz Arturo C.

Datuin Raynierson P.

Jayme Jerald F.

Matorgo Mhar Ann Kurl A.

Sapuyot Kevin C.

Tolentino Melvin M.

Submitted to: Engr. Alfredo D. Valentos, PME

Date of Submission: October 11, 2011

sample problems in industrial plant design

Documents