UNITA’ DI MISURA DESCRIZIONE

α W·m-2·K-1 coefficiente di scambio termico

β K-1 dT dρ ρ 1 −

= coefficiente di dilatazione cubica

βτ K-1 dT dε ε 1 −

= coefficiente di temperatura della permettività elettrica

γ V·m-1 rigidità dielettrica

δt m altezza dello strato limite termico

ε F·m-1 permettività del mezzo

εbulk - errore percentuale sulla temperatura del bagno

εd/Lc - errore percentuale sulla distanza tra gli elettrodo εI - errore percentuale sulla stima della corrente del

circuito di bassa tensione

εL - errore percentuale sulla stima dell’area di misura εM - errore percentuale del modulo di acquisizione εNu - errore percentuale sul numero di Nusselt

εq - errore percentuale sul flusso termico della lastra εR - errore percentuale sulla resistenza della lastra εRC - errore percentuale della resistenza campione εRTD - errore percentuale della termoresisteza εS - errore percentuale dello strumento εT K errore assoluto sulla temperatura εT% - errore percentuale sulla temperatura

εV - errore percentuale sulla tensione ai capi della

lastra

εVC - errore percentuale sulla lettura del potenziale ai

capi della resistenza campione.

ε∆T - errore percentuale sul salto di temperatura tra

fluido e parete

ζMAX m raggio dei siti attivi di nucleazione della bolla λD m lunghezza d’onda di Taylor

λH m lunghezza d’onda del getto instabile µ Kg⋅ m-1⋅ s-1 viscosità dinamica

ν m2·s-1 viscosità cinematica

ρ kg·m-3 densità di massa

E

ρ C·m-3 densità di carica caratteristica

L kg·m-3 densità del liquido ρV kg·m-3 densità del vapore σ N⋅ m-1 tensione superficiale

σE S·m-1 conducibilità elettrica

σST Ω deviazione standard (resistenza)

τ Pa tensore degli sforzi viscosi

χ parametro definito nell’equazione (1.12)

144

NUMERO ADIMENSIONALE DESCRIZIONE

Bo numero di Bond E* γ ⋅         ⋅ ⋅ = r z r HV 2 ln Ja numero di Jacob Ja* fg bulk P h T T Cp⋅( − ) = Ja** fg SAT P h T T Cp⋅( − ) = K numero di Kutateladze M parametro di mobilità Nu numero di Nusselt Pr numero di Prandtl Re numero di reynolds

145

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148

APPENDICE A