Heat Transfer Calculation In Four Different Types Of Heat Exchangers

ANSYS considers the specific heat capacity and density to be constant throughout. It disregards changes with respect to temperature. The effect of the surroundings on the heat exchanger performance was also not considered. Additionally, a mesh convergence study was not carried out. A mesh refinement analysis is imperative to conduct as it ensures results are accurate.

Aluminium Double Pipe Heat Exchanger Parallel Flow

The main aim of this experiment is to calculate the amount of heat transfer in four different types of heat exchangers. For heat transfer calculation, values of overall heat transfer coefficient, area of heat exchangers, mean temperature difference is required which is calculated from inlet and outlet temperature of hold and cold fluid measured experimentally .

• Flow rate measurement meter for both cold and hot water .
• Cold and hot water supply system. 

• Temperature measurement device for cold and holt fluid at inlet and outlet flow .
• Cross-flow Heat Exchanger
  • Number of tubes = 60 tubes
  • Length of tube = 350 mm
  • Inner tube diameter Di= 5.6 mm
  • Outer tube diameter Do= 7.0 mm
  • Thermal conductivity = 339 W/mK
• Copper Double Pipe Heat Exchanger
  • Length of tube = 1220 mm
  • Inner tube diameter Di= 13.8 mm
  • Outer tube diameter Do= 15.9 mm
  • Thermal conductivity = 339 W/mK
• Aluminium Double Pipe Heat Exchanger
  • Length of tube = 1220 mm
  • Inner tube diameter Di= 12.6 mm
  • Outer tube diameter Do= 15.9 mm
  • Thermal conductivity = 154 W/mK
• Shell and Tube Heat Exchanger
  • Number of tubes = 28 tubes
  • Length of tube = 200 mm
  • Inner tube diameter Di= 5.52 mm
  • Outer tube diameter Do= 6.35 mm
  • Thermal conductivity = 339 W/Mk

Procedure

1. For double pipe aluminium heat exchanger , set up a control valves for parallel flow with cold water in outer pipe and hot water in inner pipes .
2. Flow rates of hot and cold water should be limited to minimum value of nearly ¼ of full flow .
3. To operate the heat exchanger in steady state condition, stop the temperature variations in outlet water pipe .
4. Note down the temperature and mass flow rates from inlet and outlet water (hot and cold ) from measuring instruments .
5. Repeat the temperature and flow rate measurement for 4 different process mentioned below:-

• ¼  flow of hot water with ¼ flow of cold water
• ½ flow of hot water with ½ flow of cold water
• ¾ flow of hot water with ¾ flow of cold water
• full flow of hot water with full flow of cold water

6. For double pipe aluminium heat exchanger , set up a control valves for counter flow with cold water in outer pipe and hot water in inner pipes and repeat the process 1 to 4 for full flow .
7. For double pipe copper heat exchanger , set up a control valves for counter flow with cold water in outer pipe and hot water in inner pipes and repeat the process 1 to 4 for full flow .
8. Repeat the process 1 to 4 for shell and tube type heat exchanger as hot water in tubes and cold water in shell .
9. Repeat the process 1 to 4 for cross flow heat exchanger as hot water in tubes and cold water across the tubes .

For aluminium double pipe heat exchanger, flow between hot and cold fluid is parallel flow .The data obtained from experiment is noted down in table shown below.

Aluminium Double Pipe Heat Exchanger Parallel Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
¼ Hot / ¼ Cold	3.6	2	57.1	14.8	48.5	25.5
½ Hot / ½ Cold	7.2	4	58	16.9	51	26.8
¾ Hot / ¾ Cold	10.8	6	57.9	18	51.9	26.7
Full hot / Full cold	14.5	8	57.4	17.7	51.9	25.7

Table 1:  Aluminum Double Pipe Heat Exchanger Parallel Flow Data

For copper double pipe heat exchanger, flow between hot and cold fluid is parallel flow .The data obtained from experiment is noted down in table shown below.

Copper Double Pipe Heat Exchanger Parallel Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
Full hot / Full cold	4.5	8	57.7	18.6	53	26.8

Table 2:  Copper Double Pipe Heat Exchanger Parallel Flow Data

For copper double pipe heat exchanger, flow between hot and cold fluid is counter flow .The data obtained from experiment is noted down in table shown below.

Copper Double Pipe Heat Exchanger Counter Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
Full hot / Full cold	14.5	8	56.1	18.9	51.6	26.6

Table 3:  Copper Double Pipe Heat Exchanger Counter Flow Data

For Aluminium double pipe heat exchanger, flow between hot and cold fluid is counter flow .The data obtained from experiment is noted down in table shown below.

Aluminium Double Pipe Heat Exchanger Counter Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
Full hot / Full cold	14.5	8	58.7	19.1	53.3	26.8

Table 4:  Aluminium Double Pipe Heat Exchanger Counter Flow Data

For shell and tube type heat exchanger, flow between hot and cold fluid is counter flow .The data obtained from experiment is noted down in table shown below.

Shell and tube type Heat Exchanger Counter Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
½ Hot / ½ Cold	7.2	4	58.6	18.9	51.9	28.9
Full hot / Full cold	4.5	8	55.8	20.4	51.2	28.2

Table 5:  Shell and tube type Heat Exchanger Counter Flow Data 

For Cross flow type heat exchanger, flow between hot and cold fluid is perpendicular.The data obtained from experiment is noted down in table shown below.

Cross flow type Heat Exchanger
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
½ Hot / ½ Cold	7.2	4	56.8	17.3	49.8	27.3
Full hot / Full cold	14.5	8	56.6	18.9	50.6	28.2

Table 6:  Cross flow type Heat Exchanger Flow Data 

Calculations for heat transfer between hot and cold fluid .

 (Ahmed ,Sammarraie ,2017)

 – Heat transfer (+ ve for gained or –ve for lost) in KW

 – Mass flow rate in Kg/s

 – Specific Heat Capacity =4.18 kJ/kgK for water

 – Change in Temperature in K

Consider for aluminium double pipe heat exchanger , Heat loss and gain is calculated from values given in table below

Aluminium Double Pipe Heat Exchanger Parallel Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
¼ Hot / ¼ Cold	3.6	2	57.1	14.8	48.5	25.5

Table 7:  Aluminum Double Pipe Heat Exchanger Parallel Flow Data

All the calculations done as per above procedure and added in table .

RESLUTS

Aluminium Double Pipe Heat Exchanger Parallel Flow
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
¼ Hot / ¼ Cold	-2.157	1.491
½ Hot / ½ Cold	-3.511	2.759
¾ Hot / ¾ Cold	-4.514	3.637
Full hot / Full cold	-5.556	4.459

Table 8:  Aluminum Double Pipe Heat Exchange Parallel Flow Heat Transfer Data

Copper Double Pipe Heat Exchanger Parallel Flow
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
Full hot / Full cold	-1.473	4.570

Table 9:  Copper Double Pipe Heat Exchange Parallel Flow Heat Transfer Data

Aluminium Double Pipe Heat Exchanger Counter Flow
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
Full hot / Full cold	-5.455	4.291

Table 10:  Aluminum Double Pipe Heat Exchanger Counter Flow Heat Transfer Data

Copper Double Pipe Heat Exchanger Counter Flow
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
Full hot / Full cold	-4.546	4.291

Table 11:  Copper Double Pipe Heat Exchange counter Flow Heat Transfer Data

Shell and Tube Heat Exchanger
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
½ Hot / ½ Cold	-3.361	2.787
Full hot / Full cold	-1.442	4.347

Table 12:  Shell and Tube Heat Exchanger Heat Transfer Data

Cross Flow Heat Exchanger
Configuration	Heat Transfer (kW) (Hot)	Heat Transfer (kW) (cold)
½ Hot / ½  Cold	-3.511	2.787
Full hot / Full cold	-6.061	5.183

Table 13:  Cross Flow Heat Exchanger Heat Transfer Data

Calculations for log mean temperature difference

Formula for LMTD is given below    

are completely depend on the type of the heat exchanger  

Parallel Flow Heat exchanger	Counter Flow, Cross Flow , Shell and tube Heat exchanger
= Th, Inlet – Tc, Inlet	= Th, Inlet – Tc, Outlet
= Th, Outlet – Tc, Outlet	= Th, Outlet – Tc, Inlet

Table 14:  Heat Exchanger Temperature difference (Rennie, Vijaya ,2015)

Figure 2:  Heat exchanger temperature difference

Consider for aluminium double pipe heat exchanger ,LMTD is calculated from values given in table below

Aluminium Double Pipe Heat Exchanger Parallel Flow
Configuration	Hot Water Flow Rate (L/m)	Cold Water Flow Rate (L/m)	Hot Water Inlet Temp. (°C)	Cold Water Inlet Temp. (°C)	Hot Water Outlet Temp. (°C)	Cold Water Outlet Temp. (°C)
¼ Hot / ¼ Cold	3.6	2	57.1	14.8	48.5	25.5

Table 15:  Aluminum Double Pipe Heat Exchanger Parallel Flow Data

Copper Double Pipe Heat Exchanger Parallel Flow

LMTD calculation shown below

 = 304.67 K

All the calculations done as per above procedure and added in table .

Aluminium Double Pipe Heat Exchanger Parallel Flow	LMTD(K)
¼ Hot / ¼ Cold	304.68
½ Hot / ½ Cold	304.91
¾ Hot / ¾ Cold	304.99
Full hot / Full cold	305.48
Aluminium Double Pipe Heat Exchanger Counter Flow	LMTD(K)
Full hot / Full cold	306.04
Copper Double Pipe Heat Exchanger Parallel Flow	LMTD(K)
Full hot / Full cold	305.22
Copper Double Pipe Heat Exchanger Counter Flow	LMTD(K)
Full hot / Full cold	304.07

Table 16:  LMTD Data for parallel and counter flow

For Shell and Tube heat exchangers and Cross flow heat exchangers, a correction factor is multiplied to  LMTD formula 

f is the correction factor.

For correction factor ,values of two temperature ratios P and R need to be calculated then their intersection point on graph gives correction factor f (Panchal ,Ebert,2012).

T1 – Cold Water Inlet Temperature

T2 – Cold Water Outlet Temperature

t1 – Hot Water Inlet Temperature

t2 – Hot Water Outlet Temperature  

Calculation for shell and tube type heat exchanger 

As the getting values are coming out of graph so the correction factor is considered to be 1

 = 304.32 K

All the calculations done as per above procedure and added in table .

Shell and Tube Heat Exchanger	LMTD(K)
½ Hot / ½ Cold	304.32
Full hot / Full cold	302.17
Cross Flow Heat Exchanger	LMTD(K)
½ Hot / ½ Cold	303.98
Full hot / Full cold	303.02

Table 17:  LMTD Data for cross flow and shell and tube type heat exchanger

Calculation for area of heat exchanger

Area

Heat Exchanger Type	Area Inside m2	Area Outside m2
Aluminium Double Pipe Heat Exchanger Parallel	0.0482	0.0609
Copper Double Pipe Heat Exchanger Parallel	0.0528	0.0609
Shell and Tube Heat Exchanger	0.0971	0.111
Cross flow heat Exchanger	0.3694	0.4618

Table 18:  Inner and Outer Areas of heat exchanger

   is overall heat transfer coefficient

Calculation of overall heat transfer coefficient for aluminium heat exchanger in parallel

1.491 kW

0.0609m²

304.68 K  

80.35 W/ m² K

Overall Heat Transfer Coefficient is calculated using the formula

 (Warren ,Eckert ,2009) 

= 44.85 

All the calculations done as per above procedure and added in table .

Aluminum Parallel Flow
Cold water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Quarter Turn	80.35	101.52	44.851
Half Turn	148.57	187.72	82.933
Three quarter	195.79	247.38	109.292
full	239.66	302.81	133.780
Hot water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Quarter Turn	-116.24	-146.87	-64.888
Half Turn	-189.09	-238.91	-105.551
Three quarter	-243.05	-307.09	-135.672
full	-298.64	-377.33	-166.703

Table 18:  Aluminum Parallel Flow – Overall Heat Transfer Data

Aluminum Counter Flow (W/m2K)
	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Cold water	230.26	290.93	128.531
Hot water	-292.68	-369.80	-163.376

Table 19:  Aluminum Counter Flow – Overall Heat Transfer Data 

Copper Double Pipe Heat Exchanger Parallel Flow (W/m2K)
	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Cold water	245.87	283.58	131.690
Hot water	-79.27	-91.43	-42.458

Table 20:  Copper Parallel Flow – Overall Heat Transfer Data 

Copper Double Pipe Heat Exchanger Counter Flow (W/m2K)
	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Cold water	231.75	267.30	124.128
Hot water	-245.48	-283.14	-131.482

Table 21:  Copper Counter Flow – Overall Heat Transfer Data Table 

Shell and Tube Heat Exchanger
Cold water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Half Turn	82.50	94.30	44.003
full	129.61	148.16	69.133
Hot water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Half Turn	-99.49	-113.73	-53.067
full	-43.00	-49.15	-22.934

Table 22:  Shell and Tube Heat Exchanger – Overall Heat Transfer Data

Cross flow heat Exchanger
Cold water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Half Turn	19.85	24.82	11.029
full	37.04	46.31	20.579
Hot water	U for Inner Area (W/m2K)	U for Outer Area (W/m2K)	Overall Heat Transfer (W/m2K)
Half Turn	-25.01	-31.27	-13.897
full	-43.31	-54.15	-24.064

Table 23:  Shell and Tube Heat Exchanger – Overall Heat Transfer Data Table

Conclusion

It is concluded from the calculated results that heat transfer is maximum for counter flow heat exchanger as compared to parallel flow and cross flow .This is mainly due to highest value of log mean temperature difference for counter flow .Both the materials aluminium and copper perform equally good in transferring the heat .So combination of double pipe heat exchanger with counter flow will be optimum to use for effective heat transfer (Kay ,Nedderman ,2010) .   

References

Ahmed T. Al-Sammarraie & Kambiz Vafai (2017) ,Heat transfer augmentation through convergence angles in a pipe, Numerical Heat Transfer, Part A: Applications, 72:3, 197-214, 

Kay J M & Nedderman R M (2010) ,Fluid Mechanics and Transfer Processes, Cambridge University Press

Randall, David J.; Warren W. Burggren; Kathleen French; Roger Eckert (2009). Eckert physiology: Heat exchanger mechanisms and adaptations. Macmillan. p. 587. ISBN 0-7167-3863-5.

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E.A.D.Saunders (2015). Heat Exchangers:Selection Design And Construction Longman Scientific and Technical ISBN 0-582-49491-5

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