Armfield – Heat Transfer – HT30XC Computer Controlled Heat Exchanger Service Module

The service unit provides two fluid streams to the heat exchanger, a hot water stream and a cold water stream. The hot water stream is heated in a vessel fitted with an electric heater. The heater is switched on and off by a solid state relay (SSR) which is under software control. A thermostat limits the maximum water temperature to 85°C for operator safety. A gear pump circulates water from the vessel, through the heat exchanger and back into the heater vessel. Both the pump speed and direction are under software control, allowing for co-current and counter-current investigations over a wide range of flow rates.

The cold water stream is generated from a mains water supply. The flow through the heat exchanger is adjusted by a variable flow valve, again under software control. A manually adjustable pressure regulator is used to minimise the effect of mains pressure fluctuations.

Conditioning circuits for up to 10 K-type thermocouples are included, (the thermocouples themselves are supplied with the heat exchangers). The instrumentation also includes flow meters to measure the flow rates of the two fluid streams.

Switching on the unit puts it into ‘Standby’ mode. From this mode it is necessary for a regular series of pulses to be received from the software (via the built in USB interface) to fully power up the unit. This ensures that unless the control software is running, the heaters, the pump and the cold water control valve cannot be switched on. The unit also includes an emergency stop switch. All electrical circuits are located in a bench mounted ABS supporting base, and protected by a Residual Current Device for operator safety. The ABS base includes a drip tray and drain tap in case of water spillage or leakage.

Software Information

Educational software is provided for all Armfield heat exchangers. Included are drivers to enable other software applications to communicate with the HT30XC via the USB interfrace. Users can also write their own software typically in LabVIEW™, MatLab™, ‘C’, ‘C++’, Visual Basic™, and Delphi™, among others, to remotely coontrol the equipment, for example, over a Local Area Network (LAN) or even over the internet. The HT30XC is ideal for this, as it has been designed to shut down safely in the event of a commuincations failure. Once the heat exchanger has been installed and configured, the student does not need to be present with the equipment.

Available Models

HT31 Tubular Heat Exchanger, HT36 Extended Tubular Heat Exchanger

The tubular heat exchanger is the simplest form of heat exchanger and consists of two concentric (coaxial) tubes carrying the hot and cold fluids. In these miniature versions the tubes are separated into sections to reduce the overall length and to allow the temperature at points along both fluid streams to be measured. Two versions are available, the HT31 is a basic version with two sections and a single interim temperature measurement point. The HT36 is a more sophisticated unit with four longer tube sections, giving four times the overall heat transfer area and three interim temperature measurement points in each fluid stream.

The HT36 has sufficient heat transfer area to demonstrate the classic counter current flow conditions where the outlet of the heated stream is hotter than the outlet of the cooled stream.

Key Features

• A small-scale Tubular Heat Exchanger system for use with an Armfield Heat Exchange Service Unit to teach the fundamental concepts of heat exchangers
• Comprises a number of sections of concentric tubes, the outer section constructed from clear acrylic for visibility and the inner tube from stainless steel
• The tubes are easily dismantled for cleaning
• A comprehensive instruction manual is included

HT32 Plate Heat Exchanger, HT37 Extended Reconfigurable Plate Heat Exchanger

The plate heat exchanger is extremely versatile and commonly used in the food and chemical processing industries. Different combinations of plates and gaskets can be arranged to suit a particular application. The miniature exchanger supplied consists of a pack of plates with sealing gaskets held together in a frame between end plates. Hot and cold fluids flow between channels on alternate sides of the plates to promote heat transfer.

Key Features

• A small-scale plate heat exchanger system for use with an Armfield Heat Exchange Service Unit to teach the fundamental concepts of heat exchangers
• Comprises a number of stainless steel plates, each with a pressed chevron pattern and a food-grade silicon rubber sealing gasket, mounted in a frame
• Easily dismantled for cleaning
• A comprehensive instruction manual is included

HT33 Shell & Tube Heat Exchanger

The shell and tube heat exchanger is commonly used in the food and chemical process industries. This type of exchanger consists of a number of tubes in parallel enclosed in a cylindrical shell. Heat is transferred between one fluid flowing through the tubes and another fluid flowing through the cylindrical shell around the tubes.

The miniature exchanger supplied is designed to demonstrate liquid-to-liquid heat transfer in a 1-7 shell and tube heat exchanger (one shell and seven tubes with two transverse baffles in the shell).

Key Features

• A miniature shell and tube heat exchanger for use with an Armfield Heat Exchanger Service Unit
• Comprises an outer shell and seven internal tubes. There are two transverse baffles inside the shell
• Four temperature sensors are supplied in tappings at fluid inlets and outlets
• The heat exchanger is constructed from stainless steel tube and clear acrylic. It is mounted on a PVC baseplate, which is designed to be installed on the plinth of the Heat Exchanger Service Unit without the need for tools
• The stainless steel tubes can be removed from the heat exchanger for cleaning
• A comprehensive instruction manual is included

HT34 Jacketed Vessel with Coil & Stirrer

Vessel heating or cooling of a process liquid in a tank, either batchwise or with continuous product feed, is common practice throughout industry.

The characteristics of the heat transfer using an external jacket or internal coil can be demonstrated together with the effect of stirring the vessel contents.

Key Features

• Miniature jacketed vessel heat exchanger system for use with an Armfield Heat Exchanger Service Unit
• Comprises processing vessel with outer jacket, inner coil, variable-speed stirrer and baffle
• K-Type thermocouples measure the vessel contents and the inlet and outlet temperature of both fluid streams (6 in total)
• The Heat Exchanger is designed to be installed on the service unit without the need for tools
• A comprehensive instruction manual describing how to carry out the laboratory teaching exercises in combined radiation and convection (free and forced) and their analysis as well as assembly, installation and commissioning is included

HT35 Cross Flow Heat Exchanger

The Cross Flow Heat Exchanger is commonly used in applications such as heating, ventilating and air conditioning. It is also encountered as vehicle engine radiator.

This type of heat exchange occurs when the flow direction of the two fluids cross each other. In the HT35, hot water flows in and out of a radiator, perpendicular to air stream, which is being pulled into the radiator by an axial fan.

The convection between the two fluids through fins surface on the radiator implements the heat exchange.

Key Features

• A small-scale cross flow heat exchanger system for use with the Armfield Heat Exchanger Service unit to teach the fundamentals concepts of heat transfer
• Some parts in the heat exchanger such as probes and axial fan can be easily removed for cleaning
• The unit enables variation of the parameters involved in the cross-flow exchange process and therefore a complete analysis of the phenomena
• K-type thermocouples measure the inlet and outlet water and air temperatures, as well as permitting the connection of the air velocity sensor to the HT30XC
• The air mass flow rate is derived using an air velocity sensor
• The unit is mounted on a PVC baseplate, which is designed to be installed on the plinth of the Heat Exchanger Unit without the need for tools
• A comprehensive instruction manual is included

Key Features

HT30XC Computer Controlled Heat Exchanger Service Module

• Benchtop service unit, designed to accommodate a range of different small-scale heat exchangers
• Comprises hot water vessel, hot water recirculation pump, cold water control system, computer interface and all necessary instrumentation
• The hot water vessel is made from clear acrylic (for visibility) and includes a 2kW heater with thermostatic over-temperature cut-out and low water level detection.
• The hot water pump is bi-directional (to allow co-current and counter- current investigations without re-configuring the hardware) and the flow rate is under computer control
• The cold water system includes a manually adjustable pressure regulator and a flow control valve which is under computer control
• Flow rates for both fluid streams in excess of 5 l/min are achievable, but this may be restricted by some designs of heat exchanger (eg HT32 & HT36 Plate Heat Exchangers)
• Up to 10 temperatures (K-type thermocouples) can be monitored using the service unit. Operating range, 0-75°C, resolution 0.1°C
• Two flow meters are included, operating range 0.2 to 9 l/min resolution 0.1 l/min
• All data is available to a (user-supplied) Windows PC, via a USB interface. This computer is also used to control the flow rates, hot water temperature, and hot water direction
• Full software for educational use is included
• A comprehensive instruction manual is included