REVIEW PAPER - HEAT TRANSFER AUGMENTATION TECHNIQUE IN SOLAR AIR HEATER DUCT USING RIBS

REVIEW PAPER - ON ENHANCEMENT OF HEAT TRANSFER USING RIBS IN SOLAR AIR HEATER DUCT

OUTLINE

ABSTRACT

INTRODUCTION

LITERATURE SURVEY

CONCLUSION

REFERENCE


ABSTRACT:

A review paper is based on heat transfer augmentation technique in solar air heater duct with ribs. By conventional solar air heater the thermal efficiency is relatively low, low heat transfer coefficient between absorber plate and flowing air leads to a high temperature on the absorber plate. Ribs have been used as a tool to enhance heat transfer by increasing the level of turbulence mixing in the flow. Enhancing heat transfer surface are used in many engineering applications such as gas turbine blade cooling passages (i.e. channel/duct), air heater, heat exchanger surfaces, gas-cooled reactor fuel elements, ventilation equipment of micro-electronic systems and air conditioning/ refrigeration systems. The ribs induce the flow separation and reattachment, which break the laminar sub layer and promote local wall turbulences. The secondary flow induced by the inclined ribs can further promote the fluid mixing between the near wall region and the core region.

There are many authors used different shapes (multiple v-shaped rib, rectangle, square and circle etc.,) to improve the thermal efficiency of solar air heater duct and compared their results by Nusselt number, prandtl number, density, kinematic viscosity, angle of attack etc.,

In this paper many research author papers are reviewed and mentioned below.

INTRODUCTION:

Solar energy is the one of best renewable sources mostly abundant in our earth.  It has been used for thousands of years in many different ways by people all over the world. 

Solar air heating is a solar thermal technology in which the energy from the sun insolation is captured by an absorbing medium and used to heat air. Nowadays, the high cost of energy and material has resulted in an increased effort aimed at producing efficient heat transfer equipment’s. The heat transfer rate can be enhanced by introducing the disturbance in the fluid flow (making and breaking thermal boundary layers) but in process industries pumping power may increase significantly and ultimately the pumping cost becomes high .Therefore to achieve the desired heat transfer rate in an existing heat exchange equipment’s at an economic pumping power, several techniques have been proposed in recent years and are discussed in further sections. Heat transfer augmentation techniques refer to different method used to increase rate of heat transfer without affecting much the overall performance of the system. These techniques are used in heat exchangers.

ACTIVE TECHNIQUE:

This technique are more complex from the use and design part of view as the method requires some external power input to cause design modification and improvement of heat transfer. Various active techniques such as mechanical aids, fluid vibration, surface vibration, jet impingement.

 PASSIVE TECHNIQUE:

 This technique generally are surface geometrical to the flow channel by incorporating inserts, ribs (or) adding device. Heat transfer can be achieved by rough surface, extended surface and treated surface.

   COMPOUND TECHNIQUE:

 It is combination of both active and passive technique.

                   LITERATURE SURVEY

1. Experimental investigations of SAH duct using continuous and discrete multi V- shape rib:

Rawat, jaurker[1] et al. experimentally investigated heat transfer coefficient and thermal efficiency by providing continuous and discrete multi V –SHAPED ribs.

PARAMETERS USED

Reynolds number (Re) - 3000-15,000

Pitch distance (p\e) - 10

Relative roughness height (eh\d) - 0.06

Angle of attack - 45°, 60

 RESULTS

  In an SAH duct discrete multi V-rib gives better thermal performance than continuous rib.

2. Square duct with w-type turbulators:

Desai, yadav [2] et al. In this paper numerical analysis was carried out of three different angles of turbulators were placed in square duct with internal W-shaped ribs. It was performed by CFD (Computational Fluid Dynamics).

PARAMETERS

Rib height (e\dh) – 0.1

Pitch distance (p\e) – 10

Length of rib (L\dh) – 14

Angle of attack (α) - 60°, 45°

RESULT

  It was found that W shaped rib at 60° gives better thermal performance than 45° rib.

3.   RECTANGULAR DUCT WITH REPEATED RIBS:

Arkan [3] et al. Computational fluid was carried out to determine average heat transfer co-efficient and friction factor for turbulent flow through rectangular duct with ribs.

PARAMETERS

Reynolds number (Re) – 3800-18000

Angle of attack (α) – 45°

Pitch height (e\d) – 10mm

Rib height - 0.5-2mm

 RESULTS

It was found that repeated ribs gives better thermal performance and pressure drop increases in smooth duct while comparing with roughened duct.

4.  Numerical investigations on SAH duct using inline and  staggered pin-fin

Mohammed rayed facraqui [4] et al. A numerical study on effect of rectangular shaped ribs in different patterns on thermal performance of solar air heater (SAH) duct. They experimentally investigated on single wall arrangement, staggered arrangement and inline arrangement of ribs. 

PARAMETERS

Reynolds number (Re) - 3,000-18,000

Angle of attack (α) - 90°, 45°, 55°

Pitch height (e\d) - 10mm

Relative roughness height – 0.018-0.052

RESULTS

 It was found that inline rib gives better thermal performance of 1.82, while comparing other relative ribs.

5.   ROUND TUBE WITH STAGGERED WPT

Sompol skull Ong [5] et al.  The article deals with thermal performance and flow resistance characteristics in a turbular heat exchanger fitted with WPT (Winglet Perforated Tapes).

PARAMETERS

 Reynolds number (Re) - 4180-24,000

 Blockage ratio (BR) - 0.15

 Prandtl number (PR) – 0.5

 Pitch rib ratio (e\d) -10mm

RESULTS

 The WPT (Winglet perforated tapes) gives better efficiency of    13-15%

6. CIRCULAR TUBE HAVING TRANSVERSE RIBS

Sujaykumar, saha [6] et al. The experimental factor of Reynolds number and Nusselt number data for laminar flow of viscous oil through a circular duct having integral transverse rib roughness and fitted with twisted tapes with oblique teeth are presented.

PARAMETERS

Reynolds number (Re) - 5,000-20,000

Angle of attack – 35°, 45°, 60°

Pitch height (e\d) - 20, 13.33&10mm

Twist ratio – 2.5 & 5.0

Rib height – 0.0526, 0.07894 & 0.01052m

RESULTS

Twisted tape with oblique teeth results in combination with integral transverse ribs roughness of 45° performs significantly better than individual enhancement

7. SAH DUCT USING 60° INCLINED V- SHAPE RIB

Rawat, jaurker [7] et al. experimentally investigated heat transfer coefficient and thermal efficiency by providing 60⁰ inclined V –SHAPED ribs. They investigated the effect of heat transfer and friction factor by using transverse, inclined, V-continuous, V-discrete ribs on absorber plate in solar air heater duct.

PARAMETERS

Reynolds number (Re) - 3,000-15,000

Angle of attack (α) - 60°, 45°

Pitch height (e\d) – 10mm

RESULTS

It was found that 60° inclined V-RIBS gives better thermal performance of 3.82

8.  RECTANGULAR DUCT WITH INCLINED DISCRETE RIBS

K.R. Agarwal, B.H. Gandhi [8] et al. experimentally investigated the effect of gap in inclined rib on heat transfer and the fluid flow characteristics of heated surface.

PARAMETERS

Reynolds number (Re) - 3,000-15,000

Angle of attack (α) - 45° 

Pitch distance (e\d) - 5, 7.5, 10mm

Thickness – 6mm

RESULTS

It gives better thermal performance of heat transfer at pitch ratio of 7.5

9.   HELICAL RIB

Pong jet Promvongeet et al [9], report carried out in a double tube heat exchanger using the helical-ribbed tube fitted with twin twisted tapes have been investigated experimentally.

PARAMETERS

Reynolds number (Re) - 2.000-15,000

Pitch height (e\d) - 10mm

Rib height (e\dh) - 0.06m
Twist ratio (y) – 2.19- 9.37

 RESULTS

 It was found that twist ratio y=8 gives high thermal

Performance at lower value of Reynolds number (Re)

10.    NOZZLE RIB IN GAS TURBINE

Chandrasekhar , Bhatt [10] et al. A numerical investigations is carried out to evaluate the heat transfer characteristics of nozzle ribs in gas turbine. Single pass cooling channel in a gas turbine blade is being designed using a new type of rib is called nozzle rib.

PARAMETERS

Reynolds number (Re) - 30,000

Pitch height (e\d) - 10&5mm

Aspect ratio (AR) - 4:1

Angle of attack (α) - 45°, 60°

Hydraulic diameter (e\dh) – 0.1

RESULTS

 Fluid flow simulation results of different configurations

 Of nozzles provides better heat transfer characteristics over

 The conventional 45⁰ ribs.

CONCLUSION:
Flow over a flat plate is to study convective heat transfer and the development of velocity and thermal boundary layer. In a smooth duct there is no disturbance, the flow is laminar. For a smooth duct the heat transfer mainly depends on Reynolds number and also observes how Nusselt number varies with Reynolds number. Transitions from laminar to turbulent flow mainly depends on surface geometry, upstream velocity, inlet surface temperature, and the type of fluid.

REFERENCE

[1] Kumar A., Saini R.P., Saini J.S., (2014), “A review of thermo hydraulic performance of artificially roughened solar air heaters”, Renewable and Sustainable Energy Reviews, Vol. 37, pp. 100 – 122.

[2] Prasad B.N., Arun K., Behura, Prasad L., (2014), “Fluid flow and heat transfer analysis for heat transfer enhancement in three sided artificially roughened solar air heater”, Solar Energy, Vol. 105, pp. 27 – 35.

[3] Alam T., Saini R.P., Saini J.S., (2014), “Effect of circularity of perforation holes in V-shaped blockages on heat transfer and friction characteristics of rectangular solar air heater duct”, Energy Conversion and Management, Vol. 86, pp. 952 – 963.

[4] Bekele A., Mishra M., Dutta S., (2014), “Performance characteristics of solar air heater with surface mounted obstacles”, Energy Conversion and Management, Vol. 85, pp.603–611.

[5] Yadav A.S., Bhagoria J.L., (2014), “A CFD based thermo-hydraulic performance analysis of an artificially roughened solar air heater having equilateral triangular sectioned rib roughness on the absorber plate”, International Journal of Heat and mass transfer.

[6] Kumar S., Saini R.P., (2009), “CFD based performance analysis of a solar air heater duct provided with artificial roughness”, Renewable Energy, Vol. 34, Issue 5, pp. 1285

[7]. Prasad, K.; Mullick, S.C. Heat transfer characteristics of a solar air heater duct used for drying purposes. Appl. Energy 1983, 13, 83–93.

[8] Principles of heat and mass transfer and lecture notes on turbulence modelling Wikipedia

[9] Kumar, A., Saini, R.P., Saini, J.S., Development of correlations for Nusselt number and friction factor for solar air heater with roughened duct having Multi v-shaped with gap rib as artificial roughness, Renewable Energy, 58(2013), pp.151-163.

[10]. Chandrashekhar Bhat, Deepak P D, Ramkumar B V N, Jagannath K, Sharma S S, Achutha Kini U, (ICMAME'2013) April 29-30, 2013 Singapore, Design and analysis of nozzle ribs in gas turbine.

[11] ASHRAE Standard 93–97, Method of Testing to Determine the Thermal Performance of Solar Collector, 1977.

[12] Lewis MJ. Optimizing the thermohydraulic performance of rough surfaces. International Journal of Heat Mass Transfer (18), 1975, pp.1243–1248 

  NOMENCLATURE

Gd                    Gap distance, m

Lv                     Length of single v shape rib, m

Gd\Lv               Relative gap distance

D                       Hydraulic diameter of duct, m

e                        Rib height, m        

e\D                    Relative roughness height

fs                       Friction factor of smooth duct

f                         Friction factor of roughened duct

g                         Gap width, m

g\e                      Relative gap width

H                        Depth of duct, m

Nus                     Nusselt number of smooth duct

Nu                       Nusselt number of roughened duct

P                         Pitch of the rib, m

P\e                      Relative roughness pitch

W                       Width of the duct, m

GREEKS SYMBOL

α                     angle of attack degree

η                     Thermo – hydraulic performance parameter