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Journal of Basic and Applied Engineering Research Print ISSN: 2350-0077; Online ISSN: 2350-0255; Volume 1, Number 3; October, 2014 pp. 41-46 © Krishi Sanskriti Publications http://www.krishisanskriti.org/jbaer.html

Some Studies on the Performance of Automotive Radiator at Higher Coolant Temperature

Devendra Vashist1, Sunny Bhatia

2, Ashish Kalra

3

1,2,3Automobile Engineering Department, Manav Rachna International University

Abstract: Automotive engine cooling system takes care of excess

heat produced during engine operation. It regulates engine surface

temperature for engine optimum efficiency. Recent advancement in

engine for power forced engine cooling system to develop new

strategies to improve its performance efficiency. Also to reduce fuel

consumption along with controlling engine emission to mitigate

environmental pollution norms. This paper throws light on

parameters which influence radiator performance at high coolant

temperature that is 105o C and its effect on the effectiveness at

variable fan speed. A literature review has been done and ways

were identified how to enhance radiator performance

Keywords: Automotive engine cooling system, Performance,

Radiator

1. INTRODUCTION

The radiator plays a very important role in an automobile. It dissipates the waste heat generated after the combustion process and useful work has been done. The effectiveness with which waste heat is transferred from the engine walls to the surrounding is crucial in preserving the material integrity of the engine and enhancing the performance of the engine. Various studies have been carried out on engine radiators focusing primarily on optimizing their performance. The use of Computational Fluid Dynamics (CFD) modeling simulation of mass flow rate of air passing across the tubes of an automotive radiator was carried out [1]. Studies on the use of nano fluids in compact heat exchangers were carried out by P.Gunnasegaran et.al. [2]. Some studies to increase the rate of heat transfer were carried using twisted tape [3]. numerical study of heat transfer and pressure drop in a heat exchanger that is designed with different shape pin fins were carried out by Hamid Nabati [5]. Some studies were also carried out for Improving Radiator Efficiency by Air Flow Optimization by Salvio Chacko et.al [6]. Studies on the effect of blockage of dirt on engine radiator in the engine cooling system was carried out by S. D. Oduro [10]. Much of the work is going on to increase the value of convective heat transfer coefficient on the similar patters this work is being directed on increasing the value of h by adjusting the rpm of the fan with the help of electrical regulator/ changing the windings of the motor. Some studies were made on effects of variable mass flow rate of the coolant in the radiator, the rate of flow is controlled by the

water body pump. A test rig was developed which creates the same conditions of air flow as for a moving vehicle with variable air flow rate.

2. OBJECTIVE

Performance of engine cooling system is influenced by factors like air and coolant mass flow rate, air inlet temperature, coolant fluid, fin type, fin pitch, tube type and tube pitch etc.

While designing cooling system main aim remains that the size of the cooling system should be less but three factors does not allow the size to decrease. The factors are

1. High altitude: At high altitude, air density becomes low and hence affects air mass flow rate.

2. Summer conditions: During summer surrounding air is hot i.e. air inlet temperature is more.

3. Maximum power: Engine condition producing maximum power like when vehicle is climbing uphill, maximum heat rejection is required during this condition.

To compensate all these factors radiator core size required may be large. In this study approach has been made to increase the value of air flow rate which in turn takes care of the size of the radiator.

3. MATERIAL AND METHOD

The radiator (Fig 1) used in the study is of Maruti 800 standard type. Material of the radiator is aluminium that is why it is light in weight and less prone to corrosion.

42 Devendra Vashist, Sunny Bhatia, Ashish Kalra

Journal of Basic and Applied Engineering Research (JBAER) Print ISSN: 2350-0077; Online ISSN: 2350-0255; Volume 1, Number 3; October, 2014

Fig. 1 Radiator Fig. 2 Coolant Tank

Fig. 3 Pipes

The material used for the fabrication of the coolant tank (fig 2) is steel sheet as it can bear high temperature and its weight is moderate but less than cast iron. The operating range of the tank is 0oC to 150°C. The pipes (fig 3) used in the system should be able to bear high temperature that’s why plastic pipes and the rubber hose pipes are used in the system. Cast iron coolant pump (fig 4) is used that can operate at high temperatures and can bear thermal stresses. The pump is driven from the belt system arrangement.

Fig. 4 Water Pump Fig. 5 Electrical Switches

Fig. 6 Diameter Reducer Fig. 7 Heating Element

Anchor company switches (fig 5) are used and wooden box is used to enclose the electrical panel and heavy duty wires are used in this system to prevent the system from the failure. Diameter reducer (fig 6) is used in this system to maintain the mass flow rate of the system. The heating element (fig 7) used in the system is of the capacity 3 KW of coil shape. Thermocouples (fig 8) are used in the system for measuring the temperature of the system. The thermometer used for measuring air temperature is of the analogue type while the thermocouple having range 40oC – 120°C is used for measuring coolant temperature. A motor of 0.25HP (fig 9) is used in the system to run the water body pump.

Fig. 8 Thermocouples Fig. 9 Motor

The system used for transmitting the power from motor to water body pump is belt drive system (Fig 10) .

Fig. 10 Belt Drive System


Journal of Basic and Applied Engineering Research (JBAER)Print ISSN: 2350-0077; Online ISSN: 2350

The complete set up is shown in the figure 11.

Fig. 11 Complete set up

4. DESCRIPTION OF EQUIPMENT

Thermocouples are used for measuring the inlet and out let temperatures of the coolant that is coming outThe details of the radiator are given in the Table 1

A mixture of glycerol (Fig 12) and water was used as the coolant having a boiling point of 110C with 40% glycerol in water by volume. Data about the additive used is given below:

Formula: C3H8O3 Boiling point: 290 °C(pure) Density: 1.26 g/cm³ Melting point: 17.8 °C Molar mass: 92.09382 g/mol

Fig. 12 Glycerol-3D-balls structure


Journal of Basic and Applied Engineering Research (JBAER) 0077; Online ISSN: 2350-0255; Volume 1, Number 3; October, 2014

Thermocouples are used for measuring the inlet and out let temperatures of the coolant that is coming out of the radiator. The details of the radiator are given in the Table 1

A mixture of glycerol (Fig 12) and water was used as the coolant having a boiling point of 110C with 40% glycerol in water by volume. Data about the additive used is given below:

balls structure

5. EXPERIMENTAL PROCEDU

The radiator of the engine was 320 mm in length by 350 mm in breath as showed in Fig. 1, and had a total number of 33 tubes. All the 33 tubes were in a single row and each tube was 2 mm thick. The fins were made of aluminum alloy with a thickness of 0.8 mm, height of 20 mm and spaced 1.9 mm apart as shown in figure 1. The radiator was thorocleaned of all dust and debris before the experiments were carried.

6. ASSUMPTIONS

In order to carry out the studies following assumptions were made;

1.Constant coolant flow rate and fluid temperatures at both the inlet and outlet temperatures, that thesteady state 2.There were no phase changes in the coolant 3.Heat conduction through the walls of the coolant tube was negligible 4.Heat loss by coolant was only transferred to the cooling air, thus no other heat transfer mode such as rawas considered 5.Coolant fluid flow was in a fully developed condition in each tube 6.All dimensions were uniform throughout the radiator and the heat transfer of surface area was consistent and distributed uniformly 7.The thermal conductivity of the radiator material was considered to be constant 8.There were no heat sources and sinks within the radiator 9.There was no fluid stratification, losses and flow misdistribution. The heat transfer process in the radiator was studied as a forced convective heat transfer operation.

Table 1. Specification of Experimental Setup

Pipe diameter inlet / outlet

Thickness of 1 fin

Width of fin

Diameter of cooling pipe

Radiator core height (aluminum part only)

Radiator core length (aluminum part only)

Number of fins in single column

Number of fin columns

Total number of fins

Total number of pipes

Distance between 2 pipes

Distance between 2 fins

Diameter of fan

43

Number 3; October, 2014

EXPERIMENTAL PROCEDURE

The radiator of the engine was 320 mm in length by 350 mm 1, and had a total number of 33

tubes. All the 33 tubes were in a single row and each tube was 2 mm thick. The fins were made of aluminum alloy with a thickness of 0.8 mm, height of 20 mm and spaced 1.9 mm apart as shown in figure 1. The radiator was thoroughly cleaned of all dust and debris before the experiments were

In order to carry out the studies following assumptions were

1.Constant coolant flow rate and fluid temperatures at both the inlet and outlet temperatures, that the system operated at steady state 2.There were no phase changes in the coolant 3.Heat conduction through the walls of the coolant tube was negligible 4.Heat loss by coolant was only transferred to the cooling air, thus no other heat transfer mode such as radiation was considered 5.Coolant fluid flow was in a fully developed condition in each tube 6.All dimensions were uniform throughout the radiator and the heat transfer of surface area was consistent and distributed uniformly 7.The thermal

he radiator material was considered to be constant 8.There were no heat sources and sinks within the radiator 9.There was no fluid stratification, losses and flow misdistribution. The heat transfer process in the radiator was

heat transfer operation.

Table 1. Specification of Experimental Setup

Pipe diameter inlet / outlet 26 mm

0.8 mm

20 mm

2 mm

Radiator core height (aluminum part only) 320mm

(aluminum part only) 350mm

Number of fins in single column 180

34

6120

33

Distance between 2 pipes 7.5 mm

1.9 mm

0.27 m



Figure 13 Line Diagram

7. OBSERVATIONS

Table 2 shows the observations made when the air was passed through the radiator at variable fan motor speed. Table 3 shows the different formulas used for calculations. The speed of the fan was made variable by changing the number of windings in the fan of the motor. Figure 13 and 14 shows the

variation of temperature along the length of Heat Exchanger for the two different speeds of motor.

Fig. 14 Variation of temperature along length of radiator at 1200

rpm

Table 2 Observations from the test rig

Fan

Motor

speed

Air inlet

temperature

Air outlet

temperature

Water inlet

temperature

Water outlet

temperature

Water

Mass flow

rate

Air Mass

flow rate

Effectiv

eness

(є)

Cooling

Capacity

kW

1200 rpm 25 42 105 61 0.06kg/sec 0.201kg/sec 0.6875 11

1830 rpm 25 50 105 55 0.06kg/sec 0.306kg/sec 0.62 12.5

Fig. 15 Variation of temperature along length of radiator at 1830 rpm

0

20

40

60

80

100

120

length of HE

Tem

per

atu

re

Variation of temperature for water and

air along the length of Radiator at 1200

rpm

air inlet and outlet temperature

water inlet and out let

0

20

40

60

80

100

120

Length of Heat Exchanger

Tem

per

atu

re

Variation of temperature of water and air along the length of Radiator at 1830

rpm

Air inlet and outlet temperature

Water inlet and outlet temperature

Some Studies on the Performance of Automotive Radiator at Higher Coolant Temperature 45


A graph (fig 16) is plotted showing the variation of effectiveness and cooling capacity with the variation of air flow rate at different rpm by keeping mass flow rate of coolant constant. Air flow rate has been plotted on X- Axis and the effectiveness on y axis. The temperature of inlet air has been maintained at 25o C. By the graphs plotted it is observed that effectiveness remains same with increase in air flow rate but cooling capacity increases by 12 % with an increase in air flow rate by 52.52 % keeping the mass flow rate of the coolant constant.

Fig 16: Variation of effectiveness and cooling capacity with the variation of air flow rate

Table 3

Effectiveness of radiator (є) = ��#��&��##��"�/��&��##��"�/�� Maximaum heat transfer =

o��–��o��–�� At 1 LPM mc =

�� /U�R (for water)

Cpc = 4.18 kJ/kg K.

Cpa = 1.005 kJ/kg K.

ma = 0.201 (for 1st case) ma = 0.306 (for 2nd case)

mc = 0.06 (for 1st case) mc = 0.06 (for 2nd case)

Where mc = mass flow rate of coolant in kg/sec.

ma = mass flow rate of air in kg /s

Cpc = specific heat capacity of coolant at constant pressure in kJ/kg K.

Cpa = specific heat capacity of air at constant pressure in kJ/kg K.

tci = input temperature of coolant

tco = output temperature of coolant

tai = input temperature of air.

8. FUTURE SCOPE

8.1 Use of nano fluids

Nano particles can be dispensed in conventional heat transfer fluid such as water ethylene glycol, engine oil. It produces a new class of high efficient heat exchange fluids called Nano-fluids [2, 7, 12]. Many experimental and theoretical analyses are carried and found these new heat exchanger coolants are excellent.

8.2 Fins Shape

Many studies have showed that the fin shape affects the characteristics of the radiator [5, 12]. The fin angle effect, guide wing effect, fin width effect, fin length effect, and fin

roundness effect were studied. The guide wing effect was studied while changing the radial position and circumferential fin arc length. Narrower fins produce more heat transfer area per unit volume but worsen the fin efficiency more than the wider fins. In the S shaped fin model, the narrowest fins showed the largest heat transfer rate. A longer fin length reduces the stream bend and pressure drop that occurs because of the stream bend. The fin length effect was less than the other fin effects if uniform flow was realized in the channel. Fin roundness at the head and tail edge of the fins minimally affect the heat transfer performance but greatly affect the pressure drop performance. From the real fin shape manufactured by chemical etching, the pressure drop is increased by about 30%. Lesser fin roundness is preferred to reduce the pressure drop.

0

2

4

6

8

10

12

14

1200 1830

Cooling capacity at

different fan rpm

Effectiveness



8.3 Increasing turbulence of coolants

The effectiveness of the radiator can be increased by employing turbulence promoters [12].

8.4 Use of carbon-foam fins

One more modification which can be employed is to replace aluminum fins with carbon foam channels. Due to the thermal properties of carbon foam (k = 175-180 W/mK for carbon foam with 70% porosity), along with increasing the amount of heat rejected, we will be able to reduce the overall size of the radiator while simultaneously increasing the surface area exposed to the air, thus reducing the air side resistance [12].

9. CONCLUSION

A set of numerical data on automotive radiator using coolant operating at high temperature has been presented in the study. By the literature survey a number of recommendations have been provided for the development of a more effective and compact radiator. The same is elaborated in the section, future scope. In the performance evaluation of the radiator, a radiator is installed into a test set up and parameter of mass flow rate of air is varied its effect on the effectiveness and cooling capacity is studied. The same parameters were presented graphically and the inferences made.

REFERENCES

[1] P.K.Trivedi and N.B.Vasava Study of the Effect of Mass flow Rate of Air on Heat Transfer Rate in automobile radiator by CFD simulation using CFX International Journal of Engineering

Research & Technology (IJERT) ISSN: 2278-0181 Vol. 1 Issue 6, August – 2012.

[2] P.Gunnasegaran, N.H. Shuaib, M. F. Abdul Jalal, and E. Sandhita Numerical Study of Fluid Dynamic and Heat Transfer in a Compact Heat Exchanger Using Nanofluids International Scholarly Research Network ISRN Mechanical Engineering Volume 2012, Article ID 585496, 11 pages doi:10.5402/2012/585496

[3] Chintan Prajapati, Pragna Patel, Jatin Patel and Umang Patel, A review of heat transfer enhancement using twisted tape International Journal of Advanced Engineering Research and Studies E-ISSN2249–8974

[4] C. Oliet, A. Oliva *, J. Castro, C.D. Pe´rez-Segarra Parametric studies on automotive radiators Applied Thermal Engineering 27 (2007) 2033–2043

[5] Hamid Nabati optimal pin fin heat exchanger surface Thesis Mälardalen University Sweden School of Sustainable Development of Society and Technology 2008

[6] Salvio Chacko, Dr. Biswadip Shome, Vinod Kumar, A.K. Agarwal, D.R. Katkar, Numerical Simulation for Improving Radiator Efficiency by Air Flow Optimization

[7] The Cooling Performances Evaluation of Nanofluids in a Compact Heat Exchanger 2012 SAE International

[8] Cooling System Principles by meziere racing saldana products. [9] Pawan S. Amrutkar, Sangram R. Patil Automotive Radiator

Performance Review International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-2, Issue-3, February 2013

[10] S. D. Oduro Assessing the Effect of Blockage of Dirt on Engine Radiator in the Engine Cooling System, International Journal of Automotive Engineering Vol. 2, Number 3, July 2012

[11] James Klett, Bret Conway Thermal management solutions utilizing high thermal conductivity graphite foams

[12] JP Yadav and Bharat Raj Singh Study on Performance Evaluation of Automotive Radiator S-JPSET : ISSN : 2229-7111, Vol. 2, Issue 2 samriddhi, 2011