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Computer Controlled Tray Dryer

This small-scale benchtop tray dryer dries solids by passing a stream of hot air over trays of wet material, a method commonly used in industry. It is applicable to the unit operations laboratory and also to food technology education and research.

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UOP8MKII

HEAT AND MASS TRANSFER UNIT OPERATIONS
UOP8MkII Computer Controlled Tray Dryer – Issue 2

This small-scale benchtop tray dryer dries solids by passing a stream of hot air over trays of wet material, a method commonly used in industry. It is applicable to the unit operations laboratory and also to food technology education and research.

Ordering Specification

  • A compact desktop tray dryer suitable for laboratory use
  • Computer control of temperature and air flow rate, with sophisticated data logging and analysis software
  • Capacity: up to 2.1kg of wet material
  • Flow rates 0.4 to 3.0 m/s over trays
  • Temperatures up to 80°C at 0.4 m/s (less at higher flows)
  • Integrated electronic weight measurement to determine drying rate
  • Electronic measurement of temperature and humidity before and after the drying trays
  • Electronic measurement of air flow
  • Stainless steel construction

Features

  • Stainless steel construction
  • Computer control of air flow rate and temperature
  • Full data logging
  • Integrated electronic weight measurement to determine drying rate
  • Electronic measurement of temperature and humidity before and after the drying trays
  • Electronic measurement of air flow

 

Demonstration capabilities

  • Demonstration of drying rate regimes
  • Heat and mass transfer
  • Drying tests on solids for industrial use
  • Effect of temperature and air velocity on drying rates
  • Use of psychrometric charts

Description

The UOP8MkII comprises a square air duct fabricated from stainless steel. Air is drawn into the duct through a mesh guard and flow damper by an axial flow fan. The fan speed can be controlled to produce a range of air velocities in the duct. The air passes over an electrically heated element with electronic closed-loop control, which provides stable air temperatures at the user-selected value.

A tray carrier is located in the central section of the duct, which can hold up to three trays of material to be dried. The UOP8MkII is supplied with three lightweight coated aluminium trays suitable for food applications. The trays are inserted or removed from the duct through a latched side door with an acrylic panel for viewing purposes.

The total weight of the trays and the carrier is measured using three load cells and is displayed on the software. A graph of weight against time allows the drying regimes to be displayed and understood. From the rate of change (slope) of this graph the drying rate can be determined.

Comprehensive instrumentation is included and the measured values recorded on the computer:

  • Weight of trays plus contents (with tare function)
  • Temperature (dry bulb) and relative humidity of the heated air before the trays
  • Temperature and relative humidity of the air after passing over the trays
  • Air velocity

From each pair of temperature and relative humidity readings the full thermodynamic properties of the air can be determined using a psychrometric chart, ie the wet bulb temperature, the moisture content and the changes in enthalpy. This allows for a more in-depth analysis for project or research work, for example comparing the change in moisture content of the air with the rate of moisture loss from the trays.

The equipment requires a PC (not supplied by Armfield), running Windows 98 or above, with a USB port.

Typical drying curve, showing linear region (drying rate and output air temperature constant) followed by a slowing down of the drying rate, accompanied by an associated increase in outlet air temperature and a decrease in outlet air humidity.

Software Capability

The unit is supplied with a powerful educational software package, which includes a wide range of facilities and functions.

The computer is the primary interface between the user and the equipment. A mimic diagram displays the process in real-time with readings from the relevant sensor inputs and control outputs displayed numerically.

Results can be displayed graphically, or in tabular format, with full control over the displayed graphs, including scaling, axes and which variables are displayed.

The data is exportable to general purpose spreadsheets or word processors as applicable.

Essential Accessories

A PC running Windows 98 or above with a spare USB port (not supplied by Armfield).

Requirements

Single-phase electrical supply:
UOP8-MkII-A: 220-240V 1ph 50Hz 13A
UOP8-MkII-G: 220-240V 1ph 60Hz 13A

A transformer can be supplied for 115V operation

Shipping Specification

Volume: 0.5m3
Gross weight: 100kg

Overall Dimensions

Height: 0.325m
Length: 1.16m
Depth: 0.345m
Net weight: 25kg

Ordering codes

UOP8-MkII-A: 220-240V / 1ph / 50Hz, 13 amp
UOP8-MkII-G: 220-240V / 1ph / 60Hz, 13 amp