**4. Fluid flow and heat transfer mechanism**

The heat transfer and fluid flow mechanism in porous media is important in engineering and industrial fields such as petroleum and chemical engineering [42]. This mechanism occurs for many studies such as in microchannels and nanofluids.

## *Equation of State DOI: http://dx.doi.org/10.5772/intechopen.89919*

The active method is to add the external power to increase efficiency and heat transfer rate such as vibration. So the use of the active method must consider both

The optimization techniques of heat exchanger can be shown at three different

1. Identification of the lowest initial cost of a heat exchanger design that meets

2. Identification of a heat exchanger design that will work most acceptably over

The dissimilarities of optimization techniques levels can be understood if we list

1.The heat exchangers should be flexible enough to meet specifications process such as normal fouling transients and seasonal and diurnal changes in service

2. Special requirements as weight, length, or inventory standards are important

3.The heat exchanger must endure operation under standard and foreseeable operating conditions, maintain the mechanical stresses of manufacturing

4.The heat exchanger must be maintainable, cleaning, repair or replacement and

5.The exchanger must achieve process specifications, i.e., achieve any changes in

6.There are other requirements, such as experience, capability of operating,

The heat transfer and fluid flow mechanism in porous media is important in engineering and industrial fields such as petroleum and chemical engineering [42]. This mechanism occurs for many studies such as in microchannels and nanofluids.

the required criteria of the ideal heat exchanger as follows [41]:

for heat exchangers especially in retrofit applications.

the thermal conditions by allowable pressure drops.

maintenance personnel, and manufacturing time.

7.The exchanger should cost as little as possible.

**4. Fluid flow and heat transfer mechanism**

**154**

transport, and minimize the effects of fouling and corrosion.

its components as gaskets and tubes with minimum downtime.

3. Identification of the minimum total cost of the process by choosing heat exchangers system and auxiliary components that will make the best plant

benefit of the system and additional power cost [39].

**3.1 Optimization techniques of heat exchanger**

*Inverse Heat Conduction and Heat Exchangers*

stages as the following [40]:

the plant lifetime.

process specifications.

stream temperatures.

**3.2 Criteria of the ideal heat exchanger**

the process specifications.

Example 1: In case of study characteristics of fluid flow and heat transfer in the (100) silicon microchannel heat sink, the heat convection capabilities in the phase changes as well as in a single-phase flow and the mechanism of bubble nucleation. In the heat transfer characteristics, the results illustrate that changing in the phase process in the microchannels reduces environment working temperature and absorbs the heat. Six different microchannel geometries are selected for the heat transfer experiment as shown in **Table 2**.

**Figure 1** shows that the decreasing wall temperature phenomenon during the phase change is the same as Peng and Wang [43].

On the aspect of fluid flow characteristics, the effects of the viscosity and friction coefficient of the fluid in the microchannels are much significant than the macros. Where the specifications of the sink are registered in **Table 2**, Chip 1–4 are prepared for fluid flow experiment. The friction factor is decreasing with the power of Reynolds number as shown in **Figure 2** [44].


4.The modification of wettability and capillary wicking force surface roughness

During the last 2 years, there were some review papers which outlined the subject of boiling heat transfer using nanofluids as a new category in thermal fluids.


**Table 2.** *Specification of the sink.*

**Figure 1.** *The heat flux and channel wall temperature.*

ratio (e/DH = 0.02, 0.04 and 0.06) of helically corrugated tubes on the heat transfer enhancement, isothermal friction, and thermal performance factor in a concentric tube heat exchanger are examined. Results illustrate that the thermal performance of the corrugated tube and heat transfer are increased as compared to those of the smooth tube. The rate increase in heat transfer rate is between 123 and 232%, depending on the rib height/pitch ratios and Reynolds number. The friction factor (average) of the corrugated tube is between 1.46 and 1.93 over the smooth tube [51].

MSRKE modified Soave-Redlich-Kwong equation of state

F

R

F

R

**Abbreviations**

*Equation of State*

f v

f L

Øv

ØL

**157**

EOS equation of state BWR Benedict-Webb-Rubin RK Redlich-Kwong SRK Soave-Redlich-Kwong CEOS cubic equations of state

*DOI: http://dx.doi.org/10.5772/intechopen.89919*

p system pressure, psia Pc critical pressure, psia Pr reduced pressure, psia pi initial pressure, psia T system temperature, <sup>o</sup>

Tc critical temperature, <sup>o</sup>

Ti initial temperature, <sup>o</sup>

Tr reduced temperature, <sup>o</sup>

B second virial coefficient C third virial coefficient

x mole fraction of gas phase y mole fraction of liquid phase

state

Z compressibility factor

k equilibrium ratio for the component Kij interaction coefficient parameter

equation of state

a equation of state attraction parameter b equation of state repulsion parameter

a, b, c, A0, B0, C0 constant in Benedict-Webb-Rubin equation

<sup>i</sup> fugacity of component i in the gas phase

<sup>j</sup> fugacity of component j in the liquid phase

a, b, c, A0, B0 constant in Beattie and Bridgeman equation of state

<sup>i</sup> fugacity coefficient of component i in the vapor phase

<sup>i</sup> fugacity coefficient of component i in the liquid phase

A, B parameter in Soave-Redlich-Kwong equation of state

aTi temperature-dependent coefficient of component i m parameter in Soave-Redlich-Kwong equation of state

Zi the mole fraction of component in the mixture ZL compressibility factor of the liquid phase Zv compressibility factor of the gas phase ω a centric factor of the substance nl number of moles in liquid phase nv number of moles in gas phase

aT temperature-dependent coefficient in Soave-Redlich-Kwong

ac constant coefficient in Soave-Redlich-Kwong equation of

#### **Figure 2.**

*Exponential relations between the friction factor and the Reynolds number. Example 1: in the case of study characteristics of fluid flow and heat transfer, nanofluid is widely utilized in numerous industrial applications such as boiler tubes, evaporators, and cooling of reactors in a nuclear power plant. The main parameters that directly influence on the heat transfer performance are listed as follows [45].*

#### **Figure 3.**

*Illustration of the mechanism of flow boiling CHF using nanofluid introduced.*

Available results reported that the effect of nanoparticles on the flow boiling HTC is conflicting, but the CHF could enhance on 50%. During the boiling process, parameters such as flow pattern and pressure drop were affected by the deposition of nanoparticles [46]. Authors concluded that using nanofluids might intensify the boiling HT and CHF, depending on many parameters related to additives, nanoparticles, geometry concentration, and fluid properties [47].

Their work shows how the nanofluids can achieve high heat flux with small temperature differences throughout the boiling process, which modify the critical heat flux [48]. All article reviewers said that nanofluids is a complicated phenomenon and it is not fully understood from mechanism of boiling heat transfer and twophase flow. Collected studies show enhancement in CHF, and its improvement could achieve more than 50% [49]. HTC behavior could increase or decrease during flow boiling and pool, and it depends on several parameters related to surface texture on thermophysical properties [50]. Wang et al. shows the mechanism of depositing nanoparticles on the heating surface and creating the porous layer as shown in **Figure 3**. The results show that the CHF of flow boiling is enhanced up to 18% as compared to conventional fluid. This enhancement increases with increasing some parameters, for example, the pressure system and the channel diameter [45].

Example 2: in the case of study fluid flow and heat transfer characteristics using nanofluid in a single-phase turbulent flow by using helically corrugated tubes, pitch-to-diameter ratio (P/DH = 0.18, 0.22 and 0.27) and rib-height-to-diameter

*Equation of State DOI: http://dx.doi.org/10.5772/intechopen.89919*

ratio (e/DH = 0.02, 0.04 and 0.06) of helically corrugated tubes on the heat transfer enhancement, isothermal friction, and thermal performance factor in a concentric tube heat exchanger are examined. Results illustrate that the thermal performance of the corrugated tube and heat transfer are increased as compared to those of the smooth tube. The rate increase in heat transfer rate is between 123 and 232%, depending on the rib height/pitch ratios and Reynolds number. The friction factor (average) of the corrugated tube is between 1.46 and 1.93 over the smooth tube [51].
