**Nomenclature**

*A*: Area (m<sup>2</sup> )

*AD*: Average deviation, (( pred exp ) exp ) 1 <sup>1</sup> AD d d 100 / d *n pp p n* æ ö = -´ ç ÷ è ø<sup>å</sup> Bo *<sup>q</sup>*

*Bo*: Boiling number, fg *Gi* =


```
h: Heat transfer coefficient (kW m-2 K‐1
                                          )
```

*MD*: Mean deviation, (( pred exp ) exp ) 1 <sup>1</sup> MD d d 100 / d *n pp p n* æ ö = -´ ç ÷ è ø<sup>å</sup>


Re: Reynolds number, Re *GD* m=


### **Greek letters**

*α*: Void fraction Δ*i*: The enthalpy rise across the tube (kJ kg‐1 *µ*: Dynamic viscosity (N s m-2) *ρ*: Density (kg m‐3 ) *σ*: Surface tension (N m‐1 ) ϕ2 : Two‐phase frictional multiplier

)

)

## **Gradients and differences**

(d*p*/d*z*): Pressure gradient (N m-2 m‐1 ) (d*p*/d*z F*): Pressure gradient due to friction (N m-2m‐1
