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Nomenclature and References (Sections 3.9.1-3.9.13)
3.9.14 Nomenclature and References (Sections 3.9.1–3.9.13)
Ralph L. Webb
Nomenclature
| a | parting sheet thickness for plate-fin heat exchanger |
| a | short side of a rectangular flow passage |
| Ac | exchanger minimum free flow area |
| Af | exchanger total fin area on one side |
| Afr | exchanger total frontal area |
| b | long side of a rectangular flow passage |
| b | plate spacing (or rectangular fin height) |
| cp | specific heat at constant pressure |
| C | flow stream capacity rate (ṁ cp); Cc (cold fluid), Ch (hot fluid), Cmin (minimum), Cmax (maximum) |
| d | diameter of pin fin |
| Dh | hydraulic diameter of any internal passage (Dh = 4rh = 4Ac L /A) |
| ew | wave amplitude of wavy or herringbone fin |
| f | mean friction factor, defined on the basis of mean surface shear stress |
| F | two-phase convection multiplier defined by Figure 307.4 |
| Gc | flow stream mass velocity based on minimum flow area, ṁ cp /Ac |
| Gfr | flow stream mass velocity based on flow frontal area, ṁ cp /Afr |
| H | louver fin height (Figure 301.3) |
| Kc | contraction loss coefficient for flow at heat exchanger entrance |
| Ke | expansion loss coefficient for flow at heat exchanger exit |
| L | total heat exchanger flow length; also, flow length of uninterrupted fin |
| LL | louver length normal to air flow (Figure 301.3) |
| Lp | louver pitch or half-wave pitch of wavy or herringbone fin. |
| m | fin effectiveness parameter (2α /k δ)1/2 |
| ṁA | exchanger total heat transfer area on one side |
| ṁ | mass flow rate |
| NTU | number of heat transfer units of an exchanger (= U A /Cmin) |
| Nu | Nusselt number (α Dh /k) |
| OSF | abbreviation for "offset-strip fin" |
| pcr | critical pressure |
| pf | fin pitch; center-to-center fin pitch (see Figure 298.1) |
| pr | reduced pressure (p /pcr) |
| pw | half-wave pitch of wavy or herringbone fin |
| Δp | pressure drop |
| P | fin length from root to center |
| P | friction power expended per unit of surface heat transfer area (see Equation 302.2) |
| Pr | Prandtl number (η cp /λ) |
| q | heat transfer rate, W/m2 |
| rh | hydraulic radius (Ac L /A) |
| R | flow stream capacity rate ratio (= Cmin /Cmax) |
| Rp | empirical "roughness factor" used in Cooper boiling correlation (Equation 307.8) |
| ReDh | Reynolds number based on hydraulic diameter (Dh G /η) |
| ReLp | Reynolds number based on louver pitch (Lp G /η) |
| s | center-to-center spacing |
| S | suppression factor for convective vaporization |
| St | Stanton number (α /G cp) |
| T | temperature to any arbitrary scale |
| Tp | transverse tube pitch of a flat-tube heat exchanger (Figure 301.3) |
| U | unit overall thermal conductance |
| u | velocity |
| V | volume |
| x | axial coordinate in flow direction |
| Xtt | Martinelli parameter defined by Equation 307.6 |
| Greek Symbols | |
|---|---|
| α | convection heat transfer coefficient |
| αlo | convection heat transfer coefficient for all-liquid flow |
| β | ratio of total heat transfer area on one side of a plate-fin heat exchanger to the volume between the plates on that side |
| γ | ratio of total transfer area on one side of the exchanger to total volume for the exchanger |
| δ | fin thickness |
| Δ | denotes difference |
| ε | heat exchanger thermal effectiveness, dimensionless |
| η | dynamic viscosity |
| ηf | fin efficiency, dimensionless |
| ηs | fin surface efficiency, dimensionless |
| θ | louver angle of louver fin (Figure 301.3) |
| λ | thermal conductivity |
| ρ | density |
| σ | ratio of free-flow area to frontal area, Ac /Afr, dimensionless |
| τo | unit surface shear stress |
| (ϕlo)2 | friction multiplier [see Equation 307.12] |
| Subscripts | |
| c | cold side fluid |
| cv | convective contribution in convective vaporization; nucleate boiling contribution in convective vaporization |
| fd | fully developed condition |
| g | gas phase |
| h | hot side fluid |
| l | liquid phase |
| m | mean conditions, defined as used |
| 1 | indicate fluid 1 of a two-fluid heat exchanger |
| 2 | indicate fluid 2 of a two-fluid heat exchanger |
| i | inlet condition |
| o | outlet condition |
| max | maximum |
| min | minimum |
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