DTL sizing guide - Thermo Dynamics Ltd.

1 A Selection guide for DTL Series heat ExchangersThis is your guide to sizing and selecting DTL series heat exchangers. We recommend that you read this page completely before continuing to the step-by-step procedure on the following pages. heat Exchanger AreaFlow Head lossModifying FactorHeat Exchanger LengthLog Mean Temperature DifferenceFluid Volume Flow RatePumping PowerHeat Transfer LoadOverall heat Transfer CoefficientInlet ConditionOutlet ConditionShell SideTube SideTIPS FOR USING THIS guide :Always specify counterflow operation for maximum heat exchanger can be mounted vertically if required, however, this may require special mounting the sizing procedure suggests a non-standard length heat exchanger, use the next larger size or consider using two shorter heat rely on the copper ports to support the heat using two or more heat exchangers when.

2 A) the heat Transfer Load, Q, is greater than 400 MBtu/h,b) space for locating the heat exchanger is lim ited, orc) temperature and flow parameters are outside the recommended range for a single heat heat exchanger illustrated is com prised of two DTL series heat exchangers. The shell side flow is divided between the two heat exchangers. The full flow passes through the tube side of each heat exchanger. This plum bing arrangement is typical for oil-fired boilers, that is, where a relatively large temperature rise is required for the tube side fluid (potable water) and a relatively small temperature drop is required for the shell side flow.

3 A QUICKPICK table for heat exchanger selection is available from Thermo Dynamics for selecting these heat exchangers. For special applications not covered by this guide , contact Thermo Dynamics Ltd. for ,iTt,iTs,oTt,oHeat Exchanger #1 heat Exchanger #2 The graphs in this guide present data for specific ranges of the given parameters. Operating the heat exchanger above or below these ranges is not charts related to therm al param eters (Steps 1 through 3) are for counterflow operation of the heat exchanger.

4 Parallel flow will result in a significant reduction in thermal performance and is not worksheet is attached to this guide . Maintain this sheet as an original. Always work on a photocopySymbolsAFHLLMTDMPQUS ubscriptsiostStandard engineering symbols and subscripts have been used throughout this guide and are listed below. Units are displayed with each graph along with a table for 1 of 6 DTL HX Siz ing The DTL series heat exchanger is also capable of operating with natural circulation on the tube side.

5 A separate guide has been prepared to assist in selection of heat exchangers for these applications. Consult the Thermo Dynamics for details and technical Thornhill DriveDartmouth, Nova ScotiaCanada, B3B 1R9 Tel: (902) 468-1001 Fax: (902) 468-1002 February 1992 Thermo Dynamics Frazee AvenueDartmouth, Nova ScotiaCanada, B3B-1Z4 Tel: (902) 468 - 1001 Fax: (902) 468 - 1: Known O perating ParametersConsider the following when alloc atin g th e h e at tr an sfe r flu id s:Fluids under high pressure and/or corrosive fluids are generally circulated through the tube cleaning is recommended.

6 Mechanical cleaning is not possible with DTL Series heat viscosity fluid should be circulated on the shell side. Propylene glycol, for example, has higher viscosity than loss on the tube side of the heat exchanger is generally ten times less than the shell side head loss for equal flow ra te a note of the following parameters in the boxes provided on the Side Inlet Temperature, Ts,iTube Side Inlet Temperature, Tt,iHeat Transfer Load, QShell Side Outlet Temperature, Ts,oTube Side Outlet Temperature, Tt.

7 OUse the figures given here to determine Ts,o and Tt,o from the flow rate or vice versa. The figures are for water as the working fluid. For 50/50 or 40/60 propylene glycol/water mixtures multiply (To-Ti) by To - Ti gives a negative result then simply drop the negative sign when using the graphs at the operate within the range of parameters provided. This will ensure that flow is turbulent but not excessively ,oTs,iTs,oTt,i - Ti ( F)0204060801001201401601802002345678910M s or Mt (USGPM)400300200160120804020 heat Transfer LoadQ (MBtu/h)FromkWIGPMkg/s CToMBtu/hrUSGPMIGPM FMultiply ConversionsTo - Ti ( F)0102030405060708090101520253035404550M s or Mt (USGPM)40030020016012080 heat Transfer LoadQ (MBtu/h)page 2 of STEP 2: The O verall heat Transfer CoefficientEstimate the Degree of Fouling.

8 Light Fouling - Distilled waterModerate Fouling - Treated boiler feedwater, below 120 F (50 C)Heavy Fouling - Treated boiler feedwater above 120 F (50 C), River water, Well water, propylene glycol the overall heat transfer coeffient, U, from the appropriate graph using the shell side flow rate, Ms. Two cases are presented (A and B). Both are valid for forced circulation on the shell and tube sides the hotter fluid is circulated on the tube side, then increase U by 10%.

9 Make a note of U in the box provided on the the ratio of shell side to tube side flow rates, the factor, F, using the flow rate ratio and make a note in the box provided on the (USGPM)100150200250300350400450051015202 53035404550U (Btu/h-ft2- F)Tube Side: Water, Forced CirculationShell Side: PG/Water 50/50, Forced CirculationB2" 3" 4" " 3" 4" 4" U (Btu/h-ft2- F)2" 3" 0100200300400500600700051015202530354045 50Ms (USGPM)Tube Side: Water, Forced CirculationShell Side: Water, Forced CirculationALightMediumHeavyFromIGPMBtu/ h-ft2- FToUSGPMW/m2-KMultiply 3 of STEP 4: heat Exchanger LengthA = F x U x LM TDQ x 1000 STEP 3.

10 Log Mean Temperature Difference T2 ( F) T1 ( F)LMTD ( F) 020406080100120140160180200020406080 100 120 140 160 180 20018516514512510585654525155 Area (ft2)Length (ft)3456789101112036912 15 18 21 24 27 30 33 36 39 42 454" 3" 2" Area (ft2)Length (ft) " Frommm2 Toftft2 Divide ConversionsCalculate T1 and T2 using the equations provided on the the above calculations result in a negative value for T1 and/or T2 then simply drop the negative sign prior to using the graph at the LMTD from the graph.