l1-shell and tube heat exchanger

8/20/2019 L1-Shell and Tube Heat Exchanger

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Universiti Teknologi MARA

CPE554

Exp/HE 1

STANDARD OPERATION PROCEDURES

PLANT START-UP PROCEDUREThe following is a start-up checklist with preliminary exercises. Please go through them beforestarting any Experiment. Also refer to the P and I sketch in the Manual.

1. Switch on the main power supply to the Plant at the front of the panel.

WHENEVER ANY ANNUNCIATOR IS ACTIVATED, PRESS THE ACKNOWLEDGE(RED) BUTTON TO SILENCE THE BUZZER. RATIONALISE THE CAUSE OF THEALARM CONDITION.

2.

Switch the DP Selector Switch to the equalizing (vertical or “0”) position.

3. The manual valve at the external water supply inlet to T1 should always be opened.

4. Fill tank T1 and T2 with water to their maximum level.

5. At tank T1, shut fully the discharge valve (HV) but open fully its by-pass valve (BVH). Start

the HW pump PH for the water recirculate around its tank T1, via only BVH. The suction valve

of pump PH must remain open at all times.

6. Switch ON the heaters from the front of the panel and allow the water in tank T1 to be heated to

its maximum temperature 70°C (see TIC5).

7. Check that all the CW pumps (PC1, PC2) by-pass valves (BVC1, BVC2) and discharged valves(CV1, CV2) are opened. All suction valves for pumps PC1, PC2 and PH must remain open at

all times.8. Make sure CW pumps PC1 and PC2 are off. Note that the HW pump PH is still recirculating

HW around its tank T1 via its by-pass valve (BVH), but its discharge valve (HV) is still fully

shut.

9. Quickly check the various manual valves as follows:-

The manual by-pass valves around the control valves TSV3A and TSV3B should be alwaysshut but their adjacent manual valves should be always opened.

The bottom manual drain valves of tank T1 and T2 are always shut.

10. For details of the Experiments to be conducted, please refer to the Plant Experiment Manual of

MODEL HE12.


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CPE554

Exp/HE 2

AIM OF EXPERIMENTS: To evaluate and study the performance of the Shell and Tube Heat Exchanger at various

operating conditions.

PART I : Heat Load and Heat BalanceLMTD, Overall Heat Transfer Coefficient U.

PART II : Turbulent/Laminar FlowReynolds Number Shell SideReynolds Number Tube Side

PART III : Heat Transfer Coefficients

PART IV : Pressure DropShell Side Tube Side

A) DESCRIPTION OF EQUIPMENT The major equipment are as follows :-

I. SHELL AND TUBE HEAT EXCHANGER

The Heat Exchanger operates with heated water HW (70oC, 158oF max*) as the heatingmedium at the Tube-side and ambient or warm water CW at the Shell-side.

II. HEATING MEDIUM HW TANK TFamiliarize with the various equipment and instruments but do not operate anyequipment yet.

i. The hot water tank T1 must be filled with water up to its maximum level - the level ofits overflow drain pipe (D).

ii. An electric immersion heater in tank T1 is automatically switched off by an ON/OFF

controller TIC5 when the heated water exceeds 70oC. There will be a slight overshoot in the water temperature after the heater is switchedoff.

iii. Pump PH circulates the hot water (heating medium) HW into the tube-side of theHeat Exchanger and then returns it to tank T1. The pump should always be startedonly when the water level in tank T1 is near its maximum level and its by-pass valve(BVH) fully opened.

iv. The flowrate of HW to the Heat Exchanger can be manually regulated at the by-pass valve (BVH) with the discharge valve (HV) fully opened.


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CPE554

Exp/HE 3

v. The process conditions of the heating medium HW are monitored as follows :-

HEATING MEDIUM HW, Heat Exchanger Tube-sideProcess Variables Instrumentation

Flowrate, USGPM, FH

Pressure, psig, Inlet to Heat Exchanger

Temperature, C, Inlet, t1

Temperature, C, Outlet, t2

Pressure Drop, mm Water, DP (Tube)

FI(H)*PG-H TI1* TI2*DPI*

NOTE*: Asterisked (*) instruments are panel-mounted.

III. COLD WATER CW TANK T

Familiarize with the various equipment and instruments but do not operate anyequipment yet.

i. The larger tank is the cold water CW tank T2 .

ii. The maximum cold water level in each tank is defined by its overflow drain pipe D.External ambient water supply is permanently available to tank T2 and this inflow iscontrolled by a mechanical float and valve to ensure that its level will be maintained atits maximum level.

iii. CW heated at the shell-side of the Heat Exchanger returns to tank T2 , so that the CW

in T2 becomes warm. Excess water in T2 overflows into the drain (D).

iv. There are two similar CW pumps PC1 and PC2 pumping CW to the shell-side of theHeat Exchanger from T2 , via their respective manual discharge valves CV1, CV2.Both pumps are operated simultaneously. When only one CW pump is operated forpumping CW into the Heat Exchanger, the other CW pump is operated as a back-mixing pump with its manual discharge valve fully shut but its by-pass valve fullyopened. This is the usual mode of operation, with PC2 acting as the back-mixingpump, and its discharge valve (CV2) fully shut but its by-pass valve (BVC2) fullyopened.

By manually regulating the by-pass valve BVC1, the flowrate of the CW from pumpPC1 to the Heat Exchanger can be varied. Note that both the pump suction valves forPC1 and PC2 must remain always opened.


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CPE554

Exp/HE 4

v. The process conditions of the CW is monitored as follows :-

COLD WATER HW, Heat Exchanger Shell-side

Process Variables Instrumentation

Flowrate, USGPM, FC

Pressure, psig, Inlet to Heat Exchanger

Temperature, C, Inlet, T1

Temperature, C, Outlet, T2

Pressure Drop, mm water, DP (Shell)

FI(C)*PG-C TI3(T1)/TIC3* TI4*DPI*

NOTE*: Asterisked (*) instruments are panel-mounted. TI3(T1)/TIC3* also acts as an ON/OFF controller to direct the CW from the HeatExchanger EITHER back to T2 (Open TSV 3A/Shut TSV 3B) OR to the Drain (Shut

TSV3A/Open TSV 3B), depending on the CW outlet temperature at TE3 (T1).

IV. INSTRUMENTATION

i. Flowrates, USGPM The flowrates of CW and HW can be read from the panel-mounted digital FlowIndicators, FI(C)* and FI(H)* respectively. These flowrates are transmitted from theirrespective flowmeters FT(C) and FT(H).

The pumps should always be started with their respective by-pass valves fully open. The flowrate required is then set by regulating its by-pass valve, with the pumpdischarge valve remaining fully open. All pumps suction valves must remain fullyopened.

ii. Temperatures, oC Temperature rise in CW due to heating at the Heat Exchanger is read from thedifference between the CW outlet (TI4*, T2) and inlet (TI3*, T1) temperatures.

Similarly, the temperature drop in HW is read from the difference between the HWinlet (TI1*, t1) and outlet (TI2*, t2) temperatures.

The four temperatures are measured using Resistance Temperature Detector (RTD)elements which are tagged as TE1, TE2, TE3 and TE4. Their temperatures aredisplayed at the digital Temperature Indicators TI1*, TI2*, TI3* and TI4* respectively,all mounted at the panel. TI3* is tagged TI3(T1)/TIC3* denoting that TI3 alsohas ON/OFF control (TIC3) capabilities.

For each RUN of experiment (corresponding to pre-selected flowrates of CW i.e. FCand HW i.e. FH), a few Sets of temperature readings are to be taken with changing(usually decreasing) t1/t2. Each Set of temperature readings comprises reading T1, T2,t1 and t2 simultaneously. The technique in getting good results is to be able to read thechanging T1, T2, t1 and t2 simultaneously, at almost steady-state conditions.


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Exp/HE 5

By taking a few Sets of readings consecutively for each RUN, the best Set ofreadings can be selected to represent the RUN. The criterion for selection is

the Heat Balance test where Heat gain QC converges best to equal Heat lostQH.

iii. Pressure Drops, mm H2O; Pressures, psig The pressure drop (DP) across the Heat Exchanger Shell side is read from thedifference between the inlet and the outlet pressure of the Heat Exchanger at its CWpipeline, measured using a Differential Pressure Transmitter (DPT). The measured DPsignal is transmitted to the panel-mount indicator (DPI*). The Heat Exchanger Tubeside pressure drop is also measured using the same DPT and DPI*. A DP selectorswitch is provided at the panel to select one at a time, the measurement and display ofthe two pressure drops at the Shell and Tube sides viz either DP (Shell) or DP(Tube) at the panel-mount DPI*.

There is a pressure gauge PG-C to measure the CW pressure at the inlet to the Shell-side of the Heat Exchanger.

There is a pressure gauge PG-H to measure the HW pressure at the inlet to the Tube-side of the Heat Exchanger.

Further note that the various pressure drop tapping points are not installed directlyinside the Heat Exchanger inlet/outlet ports, to avoid excessive turbulence. Notetherefore that each measured pressure drop is due to the Heat Exchanger PLUS thoseof its inlet expansion and short pipe length AND outlet contraction and short pipe

length. The short pipe lengths include pipe elbows and Tees which also contribute topressure drop. The actual pressure drop due to the Heat Exchanger (Shell and Tubesides) should be less than those indicated by these measurements i.e.

Actual DP(Tube) = Measured DP(Tube) at DPI* DP due to the HWpiping between its tapping points and the HEinlet/outlet HW ports, which can be calculated (see Appendix section, “CORRECTION TO THEMEASUR ED DP(TUBE) AND DP(SHELL”).

Actual DP(Shell) = Measured DP(Shell) at DPI* DP due to the CWpiping between its tapping points and the HEinlet/outlet CW ports, which can be calculated (see

Appendix section, “CORRECTION TO THEMEASURED DP(TUBE) AND DP(SHELL”).


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CPE554

Exp/HE 6

B) PREPARATION PROCEDURES

Start the following preparation procedures step-by-step.

i.

Fill tanks T1 and T2 with water to their maximum level, defined by their overflow drainpipes D.

ii. At tank T1, shut fully the discharge valve (HV) but open fully its by-pass valve (BVH).Start the HW pump PH for the water to recirculate around its tank T1, via only BVH. Thesuction valve of pump PH must remain open at all times.

Switch ON the heaters at the front of the panel and allow the water in tank T1 to beheated to its maximum temperature 70°C /158°F (see TIC5), which will take about 20

minutes. Whilst waiting, proceed to (iii) below. The ON/OFF temperature controller TIC5 will automatically switch OFF the heaters in tank T1 when the heated watertemperature exceeds its preset High Limit (say 70°C), and switch them ON again when thetemperature drops below, say 0.5 ºC of its preset High Limit (i.e. below 69.5°C).

iii. CW System : Heat Exchanger Shell sideMeanwhile get familiar with the equipment, instrumentation, piping system and the variousmanual valves. The following preliminary procedures are recommended for familiarization.a) Check that all the CW pumps (PC1, PC2) by-pass valves (BVC1, BVC2) and discharge

valves (CV1, CV2) are opened. Note that the suction valves of all the pumps (PC1,PC2 and PH) must remain open at all times.

b)

Check that the external water supply to tank T2 is always available but is automaticallyshut by the mechanical float-level valve at high level in tank T2 .

Test the water availability by pushing down the float water must flow into tank T2 via the float-level valve to confirm water availability.

c) Make sure the CW pumps PC1 and PC2 are off. Note that the HW pump PH is stillrecirculating HW around its tank T1 via its by-pass valve (BVH), but its discharge valve(HV) is still fully shut.

d) Switch ON only one CW pump, say PC1 whose suction is from tank T2 . Its by-pass valve BVC1 is still fully opened.Do not operate PC2. Shut CV2 fully.Note the CW recirculation from PC1 back into tank T2 via mainly its by-pass valveBVC1 and also the Heat Exchanger return solenoid valve TSV3A.

e) Practise manipulating the by-pass valve (BVC1) to set various flowrates of CW into theHeat Exchanger from PC1 as follows:

The manual discharge valve CV1 should remain fully opened.

With BVC1 fully opened, note the CW flowrate {FC at FI(C*)}, pressure(PG-C) and Shell-side pressure drop (at DPI*). To read DP (Shell), select thesignal to DPI* using the DP Selector Switch provided at the panel, to the DP(Shell) position and wait till the reading at DPI* is almost steady.


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Exp/HE 7

Manually adjust BVC1 until FC at FI(C*) reads almost 10 USGPM. Note also

DP(Shell) and PG-C.

Shut fully the by-pass valve (BVC1) and note the increase in FC, PG-C and DP(Shell). Note the CW temperatures at the Heat Exchanger inlet (T1 at TI3*) andoutlet (T2 at TI4*).Note the Heat Exchanger pressure drop increases with flowrates.

f) Switch ON pump PC2 whose suction is from tank T2 . Open fully its manual discharge valve CV2 and by-pass valve (BVC2). Note the CW flowrate {FC at FI(C*)}, pressure(PG-C) and Shell-side pressure drop (at DPI*).

Gradually shut only BCV2 until the CW flowrate FC is about 20 USGPM.

Note FC, PG-C and DP(Shell) which increase with the flowrate FC.

g)

Open fully BVC2 but shut fully CV2 so that pump PC2 now operates only as a back-mixing pump for tank T2 . Note the drop in FC, PG-C and DP (Shell).Only pump PC1 is now pumping through the Heat Exchanger. Shut BVC1 fully formaximum flow from PC1 through the Heat Exchanger.

Switch OFF both the CW pumps PC2 and PC1.Switch the DP Selector Switch to the equalising (vertical or ‘0’) position.

iv. HW System : Heat Exchanger Tube side.

a)

b)

Note TIC5 to check if the water temperature in tank T1 is about 70 °C (158oF),

before proceeding to the next procedure (b). Note that the discharge valve (HV) ofthe HW pump PH is still shut but its by-pass valve (BVH) is fully opened.

Gradually shut the by-pass valve (BVH) fully and simultaneously open its discharge valve (HV) fully so that the maximum HW flows into the Heat Exchanger andreturn into tank T1. Read the HW flowrate {FH at FI(H)*}, pressure (PG-H) and Tube-side pressure drop (at DPI*). To read DP (Tube), select the DP signal toDPI* using the DP Selector Switch provided at the panel, to the DP (Tube) position. Wait till the DP(Tube) reading at DPI* is almost steady to take thereading.

The temperature of HW in tank T1 will drop due to heat being transferred to the'metal' body of the Heat Exchanger, even if there is no CW flow in the HeatExchanger. Note the HW temperatures at the Heat Exchanger inlet (t1 at TI1*) andoutlet (t2 at TI2*). WHENEVER THE ANNUNCIATOR TAH3 IS ACTIVATED, PRESS THERED ACKNOWLEDGE BUTTON TO SILENCE THE BUZZER.

c) Stop the HW pump PH and note the drop in FH, PG-H and DP (Tube).Switch the DP Selector Switch to the equalising (vertical or “0”) position.Note that heat from HW is now 'stored' in the Heat Exchanger tubes.Switch OFF the heaters.

d)

Proceed to (C1) PLANNING THE EXPERIMENTS.


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CPE554

Exp/HE 8

(C1) PLANNING THE EXPERIMENTSRefer to TABLE 1 and plan out the experiment strategy as follows :-

i.

RUN Ia) Run I is done at the following recommended nominal flowrates.It is NOT necessary to operate at exactly the recommended nominal

flowrates below. A deviation of 5% is acceptable for testing purposes. CW, FC : 10 USGPM HW, FH : 25 USGPM

b)

Please refer to TABLE 1. Three (3) Sets of readings are taken for every RUN.

Each Set of temperature readings consists of four readings to be takensimultaneously: CWtemperatures - inlet T1 at TI3* and outlet T2 at TI4*,HW temperatures – inlet t1 at TI1* and outlet t2 at TI2*.

c) Note that the HW temperature in tank T1 drops (note TIC5) when the heaterinput is inadequate to meet with the heat (QC) removed by CW. Hence thesecond and third Sets of temperature readings may be taken at decreasing heatload, but the water temperature at tank T1 must be at least 60 ºC.

d) Concentrate on taking the three (3) Sets of temperature, flowrate and pressuredrop readings. The pressure drop readings DP (Shell) and DP (Tube) are taken atthe panel-mount DPI*, using the DP signal Selector Switch provided. Note thatthe pressure drop depends on the flowrate and not on the temperature.

e)

Repeat the above procedure for other RUNS (II, III, etc) at the following CWand HW recommended nominal flowrates. It is NOT necessary to operate at

exactly the recommended nominal flowrates. A deviation of 5% is acceptable.Below is a summary list of the recommended nominal flowrates.

RUN CW, FC HW, FHI 10 USGPM 25 USGPMII 10 USGPM 20 USGPMIII 10 USGPM 15 USGPMIV 10 USGPM 10 USGPM V 6 USGPM 10 USGPM

Each set of flowrate readings consists of two readings:CW flowrate (FC at FI(C)*),

HW flowrate (FH at FI(H)*).

Each set of pressure drop readings consists of two readings:

DP (Shell) at DPI*, with the DP Selector Switch at the DP (Shell) position.

DP (Tube) at DPI*, with the DP Selector Switch at the DP (Tube) position.

Each set of Heat Exchanger inlet gauge pressure readings consists of tworeadings:

PG-C of CW at the CW pipeline, inlet to the Shell side of the Heat Exchanger.

PG-H of HW at the HW pipeline, inlet to the Tube side of the Heat Exchanger.


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CPE554

Exp/HE 9

(C2) EXPERIMENTAL PROCEDURES WHENEVER THE ANNUNCIATOR TAH3 IS ACTIVATED DURING THE

COURSE OF THE EXPERIMENT, PRESS THE RED ACKNOWLEDGE BUTTON TO SILENCE THE BUZZER.

With a good overview of the experiment plan detailed in C1, proceed with RUN 1 asfollows :-

i) Check that all the pump suction valves (for PH, PC1, PC2) are fully opened allthe time.

Open BVC2 fully but shut CV2 fully so that PC2 shall operate as a back-mixingpump for tank T2 in the next experiment.Open fully both CV1 and BVC1. Only PC1 shall be used here to pump CW into theHeat Exchanger in the next experiment.

Do not switch on any CW pumps (PC1, PC2) yet. Shut HV fully but open BVH fully.

Start pump PH for HW to circulate around tank T1 via only BVH.

Start the heaters and note TIC5.

When the HW in tank T1 is almost 70oC/158oF (see TIC5), open HV fully.Quickly adjust the HW flowrate to about 25 USGPM by regulating its by-pass valve BVH.

Switch ON both the CW pumps PC1 and PC2.Quickly adjust the CW flowrate to about 10 USGPM by regulating the by-pass valveBVC1.

Switch the DP Selector Switch to the DP(Shell) position.

ii ) a) Take the first Set of temperature and flowrate readings:CW: Temperature - inlet/outlet, TI3* (T1), TI4* (T2):

Flowrate FC at FI(C*)HW: Temperature - inlet/outlet, TI1* (t1), TI2* (t2) :

Flowrate FH at FI(H*)

Note that the CW inlet temperature (T1) is increasing gradually. The CW outlettemperature (T2) varies together with the HW inlet/outlet temperatures t1/t2. Itis important that all the temperature and flowrate readings be taken almostsimultaneously.

Record these readings appropriately in TABLE 1. Also record the respective inlet pressure and pressure drop of the CW and HW

flow streams. For the pressure drop readings, DP (Shell), DP (Tube) at thepanel-mount DPI*, use the DP signal Selector Switch appropriately asexplained below.

CW : PG-C; DPI * for DP (Shell) with the DP Selector Switch at the DP(Shell) position.

HW: PG-H; DPI* for DP (Tube) with the DP Selector Switch at the DP(Tube) position.


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CPE554

Exp/HE 10

To take the DP readings at DPI*, wait till they are fairly steady. Then take the DP reading at its highest reading (i.e. peak reading) just when it

starts to decrease.

b) Continue and take the second and third Sets of the above readings for RUN Iconsecutively. The last Set of temperature readings should be taken when all thetemperatures are fairly steady.

iii. RUN I is completed, with three sets of the above readings.

Stop all the CW pumps PC1 and PC2 .

Keep the Heaters ON for the next RUN.

With the HW pump PH still running, shut fully the discharge valve HV butopen fully the by-pass valve BVH.

Switch the DP Selector Switch to the equalising (vertical or “0”) position.

iv. Whilst waiting for the HW in tank T1 to be heated to about 70oC/158oF (see TIC5)for RUN II, analyse the datas by computing the QC and QH values for each of thethree (3) Sets of readings for the previous RUN I as follows:

a) For each Set of readings in RUN I, calculate the heat load QC and QH for theCW and the HW as per the formula in section (E) CALCULATION.

b) Compare the three (3) calculated values of QC and QH for RUN I. Select theSet of readings where QC is closest to QH and note them down in Table 1

and Table 2, as the selected QC and QH for RUN I. At the same time, notedown their corresponding temperatures, flowrates and pressure drops as the selected datas for RUN I. The other two Sets of datas NOT selected can berejected as they are of no further use.

c) The above selected Set of datas i.e. QC, QH, temperatures, flowrates and pressure drops for RUN I shall be used to compute the LMTD, the overallheat transfer coefficient, Reynolds numbers, individual heat transfercoefficients and the pressure drop, for RUN I.

d) Repeat for RUN II, III, IV and V at different recommended nominal

flowrates of CW(i.e. FC) and HW(i.e. FH), using the following Procedures Check-List.

To continue with the next RUN

– Check that the HW pump PH is running with BVH fully opened but HVfully shut.

– With the heaters ON, heat till the HW in tank T1 is almost 70°C/158°F(see TIC5).

– Open HV fully. Adjust the HW flowrate until FH at FI (H*) is almost at therecommended nominal flowrate for the RUN.


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Exp/HE 11

This is done by regulating the by-pass valve BVH with HV fully opened.(However, if the flowrate is still too high even when its by-pass valve is

fully open, gradually shut its discharge valve, HV, to get the required HWflowrate). – Start the CW pumps PC1, PC2 with CV1/BVC1/BVC2 fully opened but

CV2 fully shut. Note FC at FI(C*). Adjust FC to the recommended nominal flowrates for the RUN byregulating the by-pass valve BVC1 with CV1 fully opened.(However, if the CW flowrate (FC) from PC1 is still inadequate even whenits by-pass valve BVC1 is fully shut, use the second CW pump (PC2) bygradually opening CV2 and simultaneously shutting BVC2 to get therequired CW flowrate).

– Switch the DP Selector Switch to the DP(Shell) position. –

Take the various readings for the RUN. Refer to TABLE 1 of theappropriate RUN.

To end a RUN after getting 3 sets of readings

Stop all the CW pumps PC1, PC2.

Switch the DP Selector Switch to the equalising (vertical or

“0”) position.

With the HW pump PH and the heaters still ON, shut fully HV butopen BVH fully.

(C3) PLANT SHUT-DOWN PROCEDURE

When all the experimental RUNS are completed, shut down the Plant as follows:i)ii)iii)iv)

v)

Switch OFF the heaters.Check that all the pumps (PH, PC1, PC2) are switched OFF.Switch the DP Selector Switch to the equalising (vertical or ‘0’) position.Switch OFF the main power supply to the Plant at the front of the panel/ cubical.Open all the pumps suction valves, discharge valves (HV, CV1, CV2) and by-pass valves (BVH, BVC1, BVC2).


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Exp/HE 12

(D) EXPERIMENTAL RESULTS To calculate QC and QH, please refer to section (E) CALCULATION.

TABLE 1

RUN I Set 1 Set 2 Set 3

CW HW CW HW CW HW

Nominal Flow, USGPM

Actual Flow, USGPM

Temp, C/F, Inlet

Temp, C/F Outlet

FC: 10

FC: ____

TI3: T1: ____

TI4: T2: ____

FH: 25

FH: ____

TI1: t1: ____

TI2: t2: ____

10 25 10 25

Pressure, psig, Inlet

Pressure Drop, mm H2O

PG-C: ______

DP : ______(Shell)

PG-H: ______

DP : ______(Tube)

CALCULATE FOLLOWING:

Temp Change, C/F

Average Temp, °C/°F

Q, Head Load, BTU/HR

T2 - T1: ____

T2 + T1 : ___2

QC: ____

t1 - t2 : ____

t1 + t2 : ____2

QH: ____

Compute ratio QCQH

QC :QH

QC :QH

QC :QH

SELECT Set 1 or Set 2 orSet 3, based on the bestconvergence of QC and QH

i.e. QC is nearest to 1.0QH

Set 1 isSelected/Not selected

Set 2 isSelected/Notselected


For Selected Set, compute0.5 (QC + QH), BTU/HR


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Exp/HE 13

TABLE 1 (cont.)

RUN II Set 1 Set 2 Set 3

CW HW CW HW CW HW

Nominal Flow, USGPM

Actual Flow, USGPM

Temp, C/F, Inlet

Temp, C/F Outlet

FC: 10

FC: ____

TI3: T1: ____

TI4: T2: ____

FH: 20

FH: ____

TI1: t1: ____

TI2: t2: ____

10 20 10 20



PG-C: ______

DP : ______(Shell)

PG-H: ______

DP : ______(Tube)


Temp Change, C/F



T2 - T1: ____

T2 + T1 : ___

2

QC: ____

t1 - t2 : ____

t1 + t2 : ____

2

QH: ____

Compute ratio QCQH

QC :QH

QC :QH

QC :QH

SELECT Set 1 or Set 2 orSet 3, based on the bestconvergence of QC and QHi.e. QC is nearest to 1.0

QH






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Exp/HE 14

TABLE 1 (cont.)

RUN III Set 1 Set 2 Set 3

CW HW CW HW CW HW

Nominal Flow, USGPM

Actual flow, USGPM

Temp, C/F, Inlet

Temp, C/F, Outlet

FC: 10

FC: ____

TI3: T1: ____

TI4: T2: ____

FH: 15

FH: ____

TI1: t1: ____

TI2: t2: ____

10 15 10 15



PG-C: ______

DP : ______(Shell)

PG-H: ______

DP : ______(Tube)


Temp Change, C/F



T2 - T1: ____

T2 + T1 : ___

2

QC: ____

t1 - t2 : ____

t1 + t2 : ____

2

QH: ____

Compute ratio QCQH

QC :QH

QC :QH

QC :QH


QH






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Exp/HE 15

TABLE 1 (cont.)

RUN IV Set 1 Set 2 Set 3

CW HW CW HW CW HW

Nominal Flow, USGPM

Actual Flow, USGPM

Temp, C/F, Inlet

Temp, C/F, Outlet

FC: 10

FC: ____

TI3: T1: ____

TI4: T2: ____

FH: 10

FH: ____

TI1: t1: ____

TI2: t2: ____

10 10 10 10



PG-C: ______

DP : ______(Shell)

PG-H: ______

DP : ______(Tube)


Temp Change, C/F



T2 - T1: ____

T2 + T1 : ___

2

QC: ____

t1 - t2 : ____

t1 + t2 : ____

2

QH: ____

Compute ratio QCQH

QC :QH

QC :QH

QC :QH


QH






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Exp/HE 16

TABLE 1 (cont.)

RUN V Set 1 Set 2 Set 3

CW HW CW HW CW HW

Nominal Flow, USGPM

Actual Flow, USGPM

Temp, C/F, , Inlet

Temp, C/F, Outlet

FC: 6

FC: ____

TI3: T1: ____

TI4: T2: ____

FH: 10

FH: ____

TI1: t1: ____

TI2: t2: ____

6 10 6 10



PG-C: ______

DP : ______(Shell)

PG-H: ______

DP : ______(Tube)


Temp Change, C/F



T2 - T1: ____

T2 + T1 : ___

2

QC: ____

t1 - t2 : ____

t1 + t2 : ____

2

QH: ____

Compute ratio QCQH

QC :QH

QC :QH

QC :QH


QH






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Exp/HE 17

(E) CALCULATION American Engineering Units are used here since KERN and other technical datas in the

APPENDIX are in such units.

PART Ii. Heat Load and Heat Balance

This part of the calculation is to use the datas in TABLE I to check the heat load QH and QC( BTU ) and to select the set of values where QC is closest to QH.

hr

For HW: QH BTU = FH (lbm) x specific heat (BTU) x (t1 - t2 )oF.

hr hr lbmoF

For CW: QC BTU = FC (lbm) x specific heat (BTU) x (T2 - T1) oF.

hr hr lbmoF

For each run, compare the calculated values of QH and QC and select the Set oftemperature and flowrate datas where the calculated values of QH and QC are closestto each other. This selected Set of datas shall be used to represent the results of theparticular RUN, and be used for the following subsequent calculation.

ii.

LMTD

LMTD = (t1 - T2) - (t2 - T1) ,oF

ln (t1 - T2)/(t2 - T1)

R = - (T1 - T2) S = - (t2 - t1 )- (t2 - t1 ) - (T1 - t1 )

The correction factor FT for 1 Shell Pass and 2 or more Tube Passes is given in *KERNFIG18, a zeroxed copy of which is enclosed in the Appendix section.

Thus the corrected LMTD = FT x LMTD calculated above, oF.

*Kern : Process Heat Transfer

iii. Overall Heat Transfer Coefficient U

The total heat transfer area of the HEAT EXCHANGER, A = 31.50 ft2

U BTU = Q (BTU) x 1 x 1

hr.ft2.oF hr A ft2 LMTD x FT, oF

Theoretically Q above is equals to QH or QC.Otherwise there is an error in QH or QC, most probably due to errors in the temperatures andflowrates. Calculate U based on the average of the selected Set of QC and QH values for eachRUN i.e. take Q = 0.5 (QC + QH), to get an average value of U.


18/25


CPE554

Exp/HE 18

The results of the calculation are tabulated as shown in TABLE 2 below.

TABLE 2 : Calculation of Head Load, LMTD and U from PART I.

RUN QC QH 0.5(QC +QH)

LMTD x FT U

BTUHR

BTUHR

BTUHR

oF BTUhr. ft² °F

I.

II.

III.

IV.

V.

The U value calculated above shall be referred to as the 'dirty' overall heat transfer coefficient UD.


19/25


CPE554

Exp/HE 19

PART II : REYNOLDS NUMBERFor this part of the Calculation, the students are to calculate the Reynolds numbers at the Shell

and at the Tube sides i.e. Re(s), Re(t). The selected or representative Set of flowrates and temperatures obtained from each of the RUNS,from RUN I to RUN V are to be used. The Reynolds number calculated are to be tabulated in TABLE 3.

Shell-side Re(s) for CW

Re(s) = De. Gs

where de = 4 ( 1/2 PT x 0.86 PT - 1/2 do2 ) ins. Refer Kern equation 7.5.

4-------------------------------------

1/2 do

PT = Pitch = 0.81 insDe = de ft

12do = Tube outside diameter, ins.

= Viscosity, taken at the average fluid temperature in the Shell, lbmft. hr.

Gs = Ws lbm As hr. ft2

Ws = Flowrate in lbmhr

As = Shell ID x Clearance x Baffle spacePT x 144

= 6.065" x 0.19" x 3"0.81" x 144

= 0.029 ft2


20/25


CPE554

Exp/HE 20

Tube-side Re(t) for HW

Re(t) = D. Gt

where D = Tube ID = 0.04125 ft

= Viscosity, taken at the average fluid temperature in the tube, lbmft. hr

Gt = Wt lbm

At hr. ft2

Wt = Flow rate in lbmhr

At = Nos of tubes x flow area per tubeNos of tube passes

= 32 x 0.1924 ft2 2 144

= 0.02139 ft2

* It should also be shown here, at which HW flowrate is Re(t) less than 3000. Try the calculation with HW at 3.5 USGPM.

Refer to FIG26 enclosed and note the sharp rise in friction factor for laminar flow.

Refer to FIG24 enclosed and note the sharp drop in heat transfer for laminar flow.


21/25


CPE554

Exp/HE 21

PART III : HEAT TRANSFER COEFFICIENT

For this part of the Calculation, the student are to calculate the 'clean' overall heat transfercoefficient UC from the individual heat transfer coefficient ho and hi for inside and outside fluids.

The calculated results are to be tabulated in TABLE 3.

The Dirt factor Rd which is UC - UD is to be compared against say

UC x UD

0.003 hr. ft2 oF for water/water heating or cooling heat transfer.Btu

ho : BTU

hr. ft2 oF--------------------------

Please refer to Kern Fig 28, a zeroxed copy of which is enclosed in the Appendix section, tocalculate ho, at the various Reynolds number calculated in PART II.

jH = ho. De ( Cp. ) -1/3 [( )] -0.14

k (k) -1/3 [( w)] -0.14

hi : BTUhr. ft2 oF

--------------------------

Please refer to Kern Fig 24, a zerozed copy of which is enclosed in the Appendix section, tocalculate hi and hio, at the various Reynolds number calculated in PART II.

jH = hi. D ( Cp. ) -1/3 [( )] -0.14

k (k) -1/3 [( w)] -0.14

hio = hi x ID

OD


22/25


CPE554

Exp/HE 22

Rd : hr. ft2. oFBTU

---------------------------

UC = hio x ho

hio + ho

UD is established from PART I of the Calculation and tabulated in TABLE 2.

Rd = UC - UD

UC. UD

Is Rd more than 0.003 hr. ft2. oF ?BTU

Note that UC is calculated from the Heat Exchanger heat transfer coefficients (ho, hi, hio), the

Reynolds numbers (i.e. flowrates), the flowing fluids properties and the Heat Exchanger diameters.however is determined from actual heat transfer experiments at the Heat Exchanger. It is the

dirty or design heat transfer coefficient. Fouling reduces . Fouling may get worse withoperation, resulting in reduced heat transfer and increasing pressure drop (and loss of flow).

UD

UD


23/25


CPE554

Exp/HE 23

PART IV : PRESSURE DROP PART IV of the exercise is to determine the following:-

HW : The Measured Tube-side pressure drop DP (Tube) which will be corrected andis expected to be more than the Calculated Tube-side pressure drop.CW : The Measured Shell-side pressure drop DP (Shell) which will be corrected and

is expected to be more than the Calculated Shell-side pressure drop.

The students are to calculate the pressure drop at the Shell-side and at the Tube-side i.e. DP(Shell),DP(Tube). The calculated results are to be tabulated in TABLE 3. The Calculated DP(Shell) and DP(Tube) are to be compared to the Measured DP(Shell) andDP(Tube). Correction to the Measured DP(Shell) and DP(Tube) can be made.

Pressure Drop, Shell Side Refer Kern equation 7.44 or Kern Fig 29.Kern Fig 29 is enclosed in the Appendix section.

Pressure Drop Tube Side Refer to Kern equation 7.45/7.46 or Kern Fig 26/27. Kern Fig 26/27 is enclosed in the Appendix section.

The total pressure drop must include the tube side return (U-bend) pressure loss.

Pressure Drop Measurement The Shell-side and Tube-side pressure drop (DP) are measured using the Differential Pressure Transmitter (DPT) and then indicated digitally at the panel DP Indicator (DPI*). A Selector

Switch with a set of 5 solenoid valves allows both the Shell and Tube-sides pressure drop i.e. DP(Shell), DP (Tube), to be measured one at a time. Please take note of the following :-a) The differential pressure (DP) tapping points to measure the respective pressure drop

must be at the same elevation. Otherwise, the static head must be corrected.

b) To avoid excessive turbulence and vortices at the vicinity of the differential pressure (DP)tapping points, the tapping points should be located with adequate upstream/downstreamstraight pipe runs away from turbulence and vortices. The pressure drop readings will be“noisy” otherwise, especially if the flow stream has just negotiated from a change in flow areaor direction or if it is too near the pump discharge.

c)

Note the location of each pair of tapping points. The DP measured by DPT (and displayed atDPI*) is the DP of the Heat Exchanger (Shell/Tube) PLUS various pipe elbows and “tees”and pipe length. These additional DP can be much more than DP(Tube) or DP(Shell) andmust be corrected (subtracted) from the Measured DP(Tube) and DP(Shell). Please refer tothe Appendix section “CORRECTION TO THE MEASURED DP(TUBE) ANDDP(SHELL)”.

d) When there is no flow to the Heat Exchanger, the DP Selector Switch should be switched to

the equalising (vertical or ‘0’) position. The DPI* will display almost 0 mmWG 0.5% i.e. – 25 to 25 mm H2O.


24/25

T A B L E

3

R

U N

A C T U A L

F L O W

P A R T I I :

R e y n o l d s N u m b e r

P A R T I I I : H e a t T r a n s f e r C o e f f i c i e n t

P

A R T I V : P r e s s u r e D r o p

U S G P M

B T U

H r . f t 2 . F

H r . f t 2 . F

B T U

S H E L L S I D E

m m H 2 O o r p

s i

T U B E S I D E

m m H 2 O o r p s i

F C :

R e ( s )

R e ( t )

h o

h i o

U c

U D

R d

C a l c u l a t e d

M e a s u r e d

M e a s u r e d

a n d

C o r r e c t e d

C a l c u l a t e d

M e a s u r e d

M e a s u r e d

a n d

C o

r r e c t e d

F H :

I .

F C :

F H :

I I .

F C :

F H :

I I I .

F C :

F H :

I V .

F C :

F H :

V .

F C :

F H :

N O T E :

P r e s s u r e c o n v e r s i o n : 1 p s i i s 2 . 3 0 8 8 f t H

2 O o r 7 0 3 . 7 m m H 2 O , a t 6 0 ° F

CPE554 Universiti Teknologi MARA

Exp/HE 23


25/25

Universiti Teknologi MARACPE554

Exp/HE 25

APPENDIX SECTION

SOME USEFUL (APPROXIMATE) DATAS FOR WATER TEMP

C

SG(1.0 at60°F)

DENSITYlbm/ft3

DENSITYlbm/USG

VISCOSITYlbm/ft. sec

HEATCAPACITY

BTU/lbm. F

THERMALCONDUCTIVITY

BTU/hr.ft2. F/ft

71.1 61.00 8.156 2.6947 x 10-4 0.384065 0.985 61.30 8.182 2.9272 x 10-4 1.00 0.383060 61.38 8.207 3.1503 x 10-4 0.3790

54.5 0.9872 8.227 3.430 x 10-4 48.9 0.9901 61.71 8.253 3.7565 x 10-4 0.371048 3.8223 x 10-4 40 61.94 8.289 4.4083 x 10-4 35 0.995 62.06 8.296 4.8572 x 10-4 0.999 0.3605

OTHER USEFUL DATAS Assume 1 m3/Hr is 4.4 USGPM Assume 1 psi is 2.3088 ft water or 27.72 ins or 703.72 mm Water at 60°F(SG = 1.0)

CORRECTION TO THE MEASURED DP(TUBE) AND DP(SHELL) The following are the calculated piping pressure drop that must be subtracted from the MeasuredDP(Tube) and DP(Shell), to get the actual DP(Tube) and DP(Shell) of the Heat Exchanger. Notethat pressure drop increases with flowrates.

FLOWRATES CALCULATED PIPINGPRESURE DROP FOR HW

CALCULATED PIPINGPRESURE DROP FOR CW

25 USGPM/5.68 m³/Hr20 USGPM/4.55 m³/Hr15 USGPM/3.41 m³/Hr10 USGPM/2.27 m³/Hr6 USGPM/1.36 m³/Hr

2713 mm H2O1772 mm H2O1050 mm H2O521 mm H2O

-

1805 mm H2O

1198 mm H2O710 mm H2O342 mm H2O137 mm H2O

Remarks : Calculated Piping Pressure Drop for HW.Consider the two (2) tapping points to measure DP(Tube) at the HW flowstream. Between thesetapping points and the Heat Exchanger inlet/outlet ports, there are

i)

4.5 ft of 1” pipe between the HW tapping points and the Heat Exchanger inlet/outlet ports. ii) two (2) elbows which are equivalent to 2.7 ft x 2 or 5.4 ft of 1” pipe. iii) two (2) “tees” used as “L” which are equivalent to 5.6 ft x 2 or 11.2 ft of 1” pipe.

The above HW piping pressure drop due to 21.1 ft of 1” pipe is also measured together as part ofthe Measured DP(Tube). The pressure drop due to 21.1 ft of 1” pipeline at various HW flowrates can be calculated and aretabulated in the above table.

Remarks : Calculated Piping Pressure Drop for CW.Similarly for the CW flowstream, there are

i)

3 ft of 1” pipe between the CW tapping points and the Heat Exchanger inlet/outlet ports.ii) two (2) “tees” used as “L” which are equivalent to 5.6 ft x 2 or 11.2 ft of 1” pipe.

The above CW piping pressure drop due to 14.2 ft of 1” pipeline can be calculated at various CWflowrates, as tabulated in the above Table.

l1-shell and tube heat exchanger

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