Design, development and testing of a small-scale dryer for flowers and foliage

Abstract

An efficient heated-air dryer with air recirculation was designed, developed and tested. Laboratory drying tests of chrysanthemums and roses using an existing heated-air laboratory dryer were conducted to gather bench mark information needed in the conceptualization and design of the dryer. A blower volume capacity of 0.077 m3s-1 and a heater power requirement of 6.74 kW were adopted in the design. Several types of flowers, and foliage were tested using the prototype dryer. Temperature differences during continuous drying among bottom, middle and top portions of the dryer were statistically insignificant at 5% level of significance, indicating an even temperature distribution resulting in uniform drying of the product. Total energy consumptions of 296.61 kWh and 167.8k Wh were measured for drying temperatures of 80 C and 100 C, respectively. Percent air recirculation and drying capacity were highest at 100 C (92.99% and 0.348 kg H2O h -1, respectively) and lowest at 80 C (90.37% and 0.259 kg H 2O h-1, respectively). The dryer efficiency was highest at 100 C (68.2%). Heater efficiency was low due to heat losses through conduction, convection and radiation. The overall heat utilization efficiency (HUEff), however, was highest at 100 C (21.96%). The yellow pigments in roses and pachystacys, the magenta/crimson pigments in red roses, the pink pigments in bougainvillea and the chlorophyll/ green pigment in ferns and 'kamuning' were stable under heated-air drying at 80 to 100 C. In terms of drying capacity, power consumption, percent recirculation, HUEff and quality of dried plant materials, a drying temperature of 100 C is economical and recommended for use. Small-scale business for dried roses using the fabricated dryer appeared viable.

Source or Periodical Title

Philippine Agricultural Scientist

ISSN

317454

Page

409-423

Document Type

Article

Subject

Dried flowers, Dried foliage, Dryer efficiency, Heat utilization efficiency, Heater efficiency, Hot-air dryer

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