**2.2 Effect of geometry**

Heat transfer enhancement is the process of improving the rate of heat deposition or removal on a surface. It is a subject of interest to the researchers as it results in savings in energy as well as cost. Heat transfer can be enhanced by using different types of swirl generators. Geometry plays a vital role in heat transfer enhancement. Transverse ribs with twisted tape and helical tape; axial rib with screw tape; and inclined limb in cylindrical dust have been studied for friction factor and Nusselt number [4–8]. Heat transfer augmentation techniques have been used to the study the effect of heat transfer and pressure drop due to insertion of twisted tape, inclined turbulator, corrugated tube with spring tape, diamond shape cylinder, wavy turbulator for short length and full length, center-trimmed twisted tape, flow around hexagonal cylinder, wavy channel, rhombus duct, square duct, and double pipe [9–20] as shown in **Figure 1**.

### **2.3 High-speed flow**

A computational fluid dynamic (CFD) model has been developed to understand the hypersonic flow fields for reentry vehicles; facility was created for modeling

**5**

*Applications of Heat Transfer Enhancement Techniques: A State-of-the-Art Review*

*DOI: http://dx.doi.org/10.5772/intechopen.92873*

*Applications of Heat Transfer Enhancement Techniques: A State-of-the-Art Review DOI: http://dx.doi.org/10.5772/intechopen.92873*

*Inverse Heat Conduction and Heat Exchangers*

The effect of turbulence on free stream during heat transfer enhancement caused by the destruction of the viscous sublayer in the gaseous cavitation of CO2 saturated water was recognized. The influence of roughness and wall temperature on the turbulent boundary layers was investigated [1, 2]. A model was developed to evaluate fluxes in urban boundary layers using the naphthalene sublimation

Heat transfer enhancement is the process of improving the rate of heat deposition or removal on a surface. It is a subject of interest to the researchers as it results in savings in energy as well as cost. Heat transfer can be enhanced by using different types of swirl generators. Geometry plays a vital role in heat transfer enhancement. Transverse ribs with twisted tape and helical tape; axial rib with screw tape; and inclined limb in cylindrical dust have been studied for friction factor and Nusselt number [4–8]. Heat transfer augmentation techniques have been used to the study the effect of heat transfer and pressure drop due to insertion of twisted tape, inclined turbulator, corrugated tube with spring tape, diamond shape cylinder, wavy turbulator for short length and full length, center-trimmed twisted tape, flow around hexagonal cylinder, wavy channel, rhombus duct, square duct, and double

A computational fluid dynamic (CFD) model has been developed to understand the hypersonic flow fields for reentry vehicles; facility was created for modeling

**2.1 Effect of external surface**

technique [3].

**2.2 Effect of geometry**

pipe [9–20] as shown in **Figure 1**.

**2.3 High-speed flow**

**4**

#### **Figure 1.**

*Different types of vortex generators used for enhancement of heat transfer. (a) Center-cleared twisted tape [4]. (b) Spring tape insert [9]. (c) Twisted tape [10]. (d) Swirl generator [12]. (e) Twisted tape with clearance at the center [13]. (f) Wavy tape with angular cuts [14]. (g) Full-length twisted tape [16].*

**7**

*Applications of Heat Transfer Enhancement Techniques: A State-of-the-Art Review*

the projectile flight heating upon reentry. Simulation model for heat transfer due to convection and heat penetration was proposed [21], and comparative study has been conducted using of the European Atmospheric Reentry Demonstrator.

Initially, thermal characteristics in straight wall passages have been considered to analyze the heat transfer phenomenon in channel flows. Using the finite elements method, Nusselt number and friction factor were calculated for laminar regime. An investigation on laminar-turbulent transition inside a heated horizontal tube was conducted [22]. An analytical study for joule heating in a parallel plate channel with thermally developed flow has been conducted [23]. A circular tube was examined using various different conditions for viscous flow [24]. A novel method was developed for evaluating the Nusselt number for hydrodynamic flow conditions [25]. Horizontal, inclined channels and vertical plane passages were examined for mixed convective heat transfer [26, 27]. A prediction was presented for Nusselt number for

The study of fine scale heat transfer was done with various channel configurations. 3D flow and heat transfer were examined in microchannels [29]. Theoretical analysis for heat transfer in laminar flow between two parallel plates separated by a very small space in micron range was conducted. The momentum and energy equations are solved for the hydraulic and fully developed thermal flow in the microchannel [30]. This method was also used to simulate rarefied gas flow and heat transfer in microchannels in a particular Knudsen number range [31]. Water was used as the working fluid in microchannel of rectangular shaped heat sinks, and computational studies were carried out [32]; also, their thermal performance was optimized minus water [33]. Convective heat transfer of fully developed flow both thermally and hydrodynamically in a rectangular microchannel is investigated [34]. A simulation model of low-power microchannel thermal reactor was presented [35]. Fractal branching used for the cooling of electronic chips was investigated [36]. Slotted microchannels were studied analytically on the basis of conduction and convection [37]. The performance

A variety of papers covering numerous geometries have been taken into consideration in this section. Narrow-spaced fuel element configuration in multichannel was modeled numerically [39]. Rhombus and ellipse shape ducts were studied using Galerkin integral method [40, 41]. The heat transfer in a pin fin at the end of the wall was investigated [42]. The heat transfer in a milliscale thrust nozzle was studied numerically [43]. Viscous flow convections and heat transfer were studied in corrugated ducts [44]. For square ducts a combined study was undertaken to understand the thermal characteristics in different shapes [45]. Experimental study was done with regard to two-pass internal coolant passages in gas turbines [46]. An increase in heat transfer due to rolling and pitching action in swirling ducts was found experimentally [47]. Flow and heat transfer for metal honeycomb geometry was inspected [48]. The effect of viscous forced convection in branching ducts was studied [49].

*DOI: http://dx.doi.org/10.5772/intechopen.92873*

the in-tube cooling of supercritical carbon dioxide [28].

of thermal fluid in a small capillary was studied experimentally [38].

**3. Channel flows**

**3.1 Straight wall passage**

**3.2 Microscale heat transfer**

**3.3 Irregular geometries**

the projectile flight heating upon reentry. Simulation model for heat transfer due to convection and heat penetration was proposed [21], and comparative study has been conducted using of the European Atmospheric Reentry Demonstrator.
