Acid condensation and heat transfer characteristics on H-type fin surface with bleeding dimples and longitudinal vortex generators

Abstract

Acid condensation rate is an important factor denoting the acid corrosion, and the reduction of the acid condensation can significantly relieve the acid corrosive effect on the wall surface and improve the security of the equipments. In this study, the characteristics of both heat transfer and acid condensation of the finned tube in heat exchanger were numerically studied. In the numerical model, we simulated the acid condensation by considering the vapor–liquid equilibrium effect and multi-component diffusion effect. Based on the H-type finned oval tube, we proposed three novel types of fins to both enhance the heat transfer and reduce the acid condensation. The parametric effects of gas temperature, acid vapor concentration, water vapor concentration, and Reynolds number were investigated on different fin structures. The results show that the tube bank with the new structured fins can improve the performance on both heat transfer and acid anti-condensation.

Appendix

A :

Area (m²)

a _i , b _i , c _i :

Ideal-gas heat capacity coefficients

$\bar{a}_{i}$ :

Activity

$C_{{1\upvarepsilon}} ,C_{{2\upvarepsilon}}$ :

Turbulence model constants

c _p :

Specific heat (J kg⁻¹ K⁻¹)

$\bar{C}_{{{\text{p}}i}}^{\text{l}}$ :

Partial-molar heat capacity (J mol⁻¹ K⁻¹)

D _i,m :

Effective diffusion coefficient for species i (m² s⁻¹)

D _ij :

Binary diffusion coefficient (m² s⁻¹)

Eu :

Euler number

f :

Friction factor

G _k :

Generation of turbulence kinetic energy

h :

Heat transfer coefficient (W m⁻² K⁻¹)

ΔH ^v _i :

Heat of vaporization (J mol⁻¹)

k :

Turbulent kinetic energy (m² s⁻²)

K ₀, K ₁ :

Equilibrium constants

$\bar{L}_{i}^{\text{l}}$ :

Partial-molar enthalpy (J mol⁻¹)

m _i :

Mass condensation rate of i component (kg m⁻² s⁻¹)

M :

Molar mass (kg mol⁻¹)

N :

Number of tube bank

Nu :

Average Nusselt number

p _i :

Monomer partial pressure (Pa)

p _io :

Apparent partial pressure (Pa)

P :

Pressure (Pa)

PEC:

Evaluation parameter of a heat transfer unit

Δp :

Pressure drop (Pa)

Pr :

Prandtl number

R _a :

Sulfuric acid condensation rate (mol m⁻² s⁻¹)

Re :

Reynolds number

R _w :

Water condensation rate (mol m⁻² s⁻¹)

r _i :

Latent heat of i component (J kg⁻¹)

Sc _t :

Turbulent Schmidt number

S _e :

Energy source term (J m⁻³ s⁻¹)

ΔS ^v _i :

Entropy of vaporization (J mol⁻¹ K⁻¹)

S _m :

Species source term (kg m⁻³ s⁻¹)

T :

Temperature (K)

U :

Velocity vector (m s⁻¹)

V :

Grid volume (m³)

x _a :

Sulfuric acid vapor mole fraction in gas phase

x _w :

Water vapor mole fraction in gas phase

y _i :

Mole fraction of i component in solution

Y _i :

Mass fraction of i component

ϕ _io :

Apparent fugacity coefficient

λ :

Thermal conductivity (W m⁻¹ K⁻¹)

υ :

Kinematic viscosity (m² s⁻¹)

ρ :

Density (kg m⁻³)

α _i :

Partial-molar heat capacity coefficient (J mol⁻¹)

ɛ :

Turbulent energy dissipation rate (m² s⁻³)

η _t :

Turbulent viscosity (kg m⁻¹ s⁻¹)

$\alpha_{k} ,\alpha_{\varepsilon}$ :

Inverse effective Prandtl numbers for k and ɛ

a:

Sulfuric acid

g:

Flue gas

in:

Inlet

out:

Outlet

w:

Wall or water