Conclusions

For better environment and sustainability it is really important to improve food drying systems and processes and their efficiencies. This chapter presents an ex-

ergy analysis of drying process of broccoli florets in a heat pump conveyor dryer.

Some concluding remarks are drawn from this study as follows:

• Exergy efficiency and the improvement potential rate of the drying chamber vary from 14.79% to 76.58% and 13.86 kW to 19.29 kW, respectively.

• Exergy loss of this system increases with raising the temperatures of drying air, when exergy destruction was decreased at 0.5 m/s drying air velocity.

• The maximum exergy efficiency value becomes 76.58% at a drying air temperature of 45oC and a velocity of 1.5 m/s.

Acknowledgments

The authors are grateful for the financial support provided for the project entitled "Design, test and performance evaluation of a gas engine driven solar assisted band conveyor heat pump drying system" under Project No. 106M482 by The Scientific and Technological Research Council of Turkey (TUBITAK).

Nomenclature

C Specific heat (kJ/kg oC)

E Net energy transfer rate (kW)

Ex Exergy rate (kW)

h Specific enthalpy (kJ/kg)

IP Rate of improvement potential (kW)

Q Heat transfer rate (kW)

P Pressure (kPa)

R Gas constant (J/kg oC)

S Entropy rate (kJ/s oC)

s Specific entropy (kJ/kg oC)

T Temperature (oC)

X Weight fraction of dry matter

V Air velocity (kg/s) Greek Symbols n Exergy efficiency

W Specific flow exergy (kJ/kg)

( Specific humidity (g/g) Subscripts

0 Restricted dead state a Air b Boundary c Carbohydrate dest Destroyed, destruction evap Evaporation ex Exergetic, exergy f Fat fi Fiber gen Generation p Protein v Vapor w Water da Drying air m Material [email protected] Saturated

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