HEAT TRANSFER AND THERMODYNAMICS
HT10XC Computer Controlled Heat Transfer
Teaching Equipment - Issue 4
The Armfield HT10XC is a service unit, which can be used in conjunction with a range of small-scale accessories for a wide range of demonstrations into the modes of heat transfer. The factors that affect heat transfer can be investigated and some of the practical problems associated with the transfer of heat can be clearly demonstrated.
The heat transfer accessories may be individually connected to the HT10XC service unit, which provides the necessary electrical supplies and measurement facilities for investigation and comparison of the different heat transfer characteristics.
A specific feature of the HT10XC is that it incorporates the facilities and safety features to allow the accessories to be remotely controlled from an external computer, where this is appropriate. With suitable (user provided) software, this means that the equipment can be operated remotely, for instance over an intra-net or even over the internet. All the facilities can also be accessed locally using the front panel controls and display.
Below: HT10XC - Service Unit shown with the HT11C Computer Controlled Linear Heat Conduction Accessory installed
- A benchtop service unit designed to interface to a range of heat transfer accessories
- Provides a variable, stabilised 0-24V DC supply to the heater of the heat transfer accessory, with a current capability of 9 amp
- Provides a drive signal for a proportioning solenoid valve used for flow control
- Provides a control signal to a variable speed blower used for generating airflow
- 10 temperature inputs and conditioning circuits for K-type thermocouples:
- 9 off, 0-133°C, resolution <0.1°C
- 1 off, 0-500°C, resolution <0.15°C
- Instrumentation inputs for heater voltage, heater current, air flow, water flow, radiation and light meter
- Integral USB interface, and educational software for all accessories
- Outputs can be controlled manually from the front panel, or controlled by the software from a user supplied PC
- Watchdog circuit for operator and equipment safety in case of computer or interface failure when being controlled remotely(e.g. over a network or the internet using user written software)
- Easy interfacing to 3rd party software eg LabView, MatLab
- A comprehensive instruction manual describing how to carry out the laboratory teaching exercises in non-steady state heat transfer and their analysis as well as assembly, installation and commissioning is included
- Small-scale, benchtop equipment
- Common service unit avoids unnecessary cost duplication for control and instrumentation
- Multiple accessories available covering a wide range of heat transfer investigations
- Computer control of heaters, water flow, air flow, with safety functions implemented to allow for remote operation
- Improved accuracy for quantitative results which can be related directly to theory
- Integral USB interface
- Full educational software, with data logging, control, graph plotting, and detailed ‘Help’ facility
The following heat transfer accessories are available for use under manual control:
HT11: Linear Heat Conduction
HT12: Radial Heat Conduction
HT13: Laws of Radiant Heat Transfer and Radiant Heat Exchange*
HT14: Combined Convection and Radiation
HT15: Extended Surface Heat Transfer
HT16: Radiation Errors in Temperature Measurement
HT17: Unsteady State Heat Transfer*
HT19: Free & Forced Convection
HT20: Conductivity of Liquids and Gases
In addition the following accessories can be used in computer control and remote control applications:
HT11C: Computer-Controlled Linear Heat Conduction
(material samples still need changing manually)
HT12C: Computer-Controlled Radial Heat Conduction
HT14C: Computer-Controlled Combined Convection and Radiation
HT15: Extended Surface Heat Transfer
HT16C: Computer-Controlled Radiation Errors in Temperature Measurement
HT18C: Thermo-Electric Heat Pump
HT20C: Conductivity of Liquids and Gases
*NOTE: The HT13 and the HT17 are not suitable for computer control due to
the amount of manual intervention required. The standard HT15 can be used for
computer control as no manual intervention is required.
The service unit is housed in a robust steel enclosure and designed for use on a bench or table. It provides control outputs to the accessories, and instrumentation inputs from the accessories.
- A stabilised, variable DC supply to the heater of the heat transfer accessory under evaluation
- Drive to flow-regulation valves on HT11C and HT12C
- Drive to the variable-speed air blowers used on HT14C and HT16C
Inputs and Instrumentation:
- Temperatures: (up to 10 off, dependant on accessory being used)
- Heater voltage: (All accessories except HT17)
- Heater current: (All accessories except HT17)
- Heat radiated: (HT13)
- Light radiated: (HT13)
- Air velocity: (HT14, HT14C, HT16, HT16C,HT19)
- Cooling water flowrate: (HT11C, HT12C, HT18C)
In manual mode, the outputs listed above are under control of potentiometers on the front panel of the unit. In remote mode the outputs to the accessories are controlled by the computer. A ‘Watchdog’ system is implemented in remote mode to ensure operator and equipment safety in event of a computer or communications failure.
In both modes the signals from the accessory can be shown on the front panel displays. Selector switches are used to select the chosen signal onto one of the two displays. These signals are also available on the USB interface for datalogging on the computer (even if the computer is not controlling the equipment).
Full educational software is provided with the HT10XC for all the Armfield heat transfer accessories. Separate programs are provided for each accessory, and each program contains a selection of separate exercises that can be performed. The actual details are exercise specific, but typically the following interfaces are available:
- All the temperatures and other signals such as flow rates, heater voltage and current, etc are displayed on a diagrammatic representation of the equipment
- A software ‘button’ switches the equipment from ‘standby’ mode to fully on
- The control outputs are operated by using up/down arrows or typing in a value between 0 and 100%. The sensor values can be read directly in engineering units
- Data from the sensors is logged into a spreadsheet format, with operator control over the sampling intervals (or ‘single-shot’)
- Sophisticated graph-plotting facilities are provided, including plotting of both measured and calculated values. Comparisons between data taken on different runs can be displayed. Also the graphs update in real-time as the samples are being taken
- Student questions and answers, including a layered ‘Hint’ facility
- Processing of measured values to obtain calculated values – this can be linked to the questions and answers to ensure student understanding
- The data samples can be saved, or exported in Microsoft Excel format
- Data from the sensors can be displayed independently from the data logging. This can be in bar-graph format, or a recent history graphical display – useful to check for temperature stability prior to taking a sample
- Presentation screens are available, giving an overview of the software, the equipment, the procedure and the associated theory. This is backed up by a detailed ‘Help’ facility giving in-depth guidance and background information
User Defined Software and/or Remote Operation
Included separately on the software CD are the drivers required to enable other software applications to communicate with the HT10XC via the USB system. This enables users to write their own software instead of using the Armfield-provided software. This software can be written in many different formats, typically LabVIEWTM, MatLab, ‘C’, ‘C++’, Visual Basic, Delphi, and any other software environment, which allows calls to external drivers can be used.
In this way users can write software to suit their specific requirements, in an environment they are fully familiar with and which is compatible with their other equipment.
An extension of this methodology enables the equipment to be operated remotely, such as over a local area network (LAN) or even over the internet. The HT10XC is ideal for this remote operation as it has been designed to ensure that the unit shuts down safely in the event of a communications failure. It has also been designed so that once the heat transfer accessory has been installed and configured, all the controls to perform a series of investigations are under software control, and so the student does not need to be present with the equipment.
In a typical installation, the HT10XC would be connected to a local PC via the USB bus. The local PC would be connected to the users’ PCs via LAN. The operator interface software would be run on the remote (user’s) PC and communicate to the control software on the local PC.
(Note, Armfield do not provide the software to implement this type of system).
For remote use, the appropriate heat transfer accessory would be connected to the service unit and the unit switched on. It remains in ‘standby’ mode until appropriate software is run requesting the unit to power up. The functions, which can be implemented remotely, are dependent on the accessory being used. For some accessories the configuration has to be manually implemented locally. Eg on HT11C, the required material sample has to be inserted manually. However, once this has been done, a full set of investigations can be performed for that configuration remotely.
Single-phase electricity supply:
(Current figures are worst-case figures, including
the supply to appropriate accessory)