Heat Pump Drying of Fruits and Vegetables: Principles and Potentials for Sub-Saharan Africa

Table 1

Comparison of HPD with other commonly used dryers.

Item	HPD drying	Hot air drying	Vacuum drying	Freeze drying
SMER (kg/kWh)	1.0–4.0	0.1–1.3	0.7–1.2	0.4 and lower
Operating temperature range (°C)	−10 to 80	40 to very high	30–60	−35 to >50
Operating % RH range	10–80	Varies depending on temperature	Low	Low
Drying efficiency (%)	Up to 95	35–40	Up to 70	Very low
Drying rate	Faster	Average	Very slow	Very slow
Capital cost	Moderate	Low	High	Very high
Running cost	Low	High	Very high	Very high
Control	Very good	Moderate	Good	Good

Source: Mujumdar and Jangam [20].