This system allows the study of refrigeration systems and the implementation of the thermodynamic calculations applied to refrigeration. Its uniqueness is that it is fully controllable via the Internet directly from a web browser like Internet Explorer or Firefox.
It consists of two cold rooms, each with their own evaporator but sharing the same cooling fluid R134a system (compressor, condenser …).
The control and configuration of this system can be done in two ways:
- a classic console coupled to a regulator
- PLC type industrial PAC (programmable automation controller) Compact Fieldpoint
The Compact Fieldpoint adds the possibility of remote control via the Internet, viewing the evolution curves of temperature, air and refrigerant fluid, pressure and power at various points. This allows calculating the required cooling system features such as enthalpy, entropy, Mollier diagram and performance coefficients.
Hardware
The software is embedded in a Compact Fieldpoint controller from National Instruments. It includes a RJ45 Ethernet connector that allows to connect to the network in aim of uploading the executable on the controller module to the embedded FTP and publish shared variables on the network. We use Compact Fieldpoint module inputs / outputs, analog and relays for sending commands (start / stop, compressor speed , refrigerant solenoid valves, condenser and evaporator fans, lights and heaters for cold rooms) and collect measurements. We measure the power consumed by the compressor with the power meter included in the regulator. This regulator communicates only by Jbus protocol. So we use the RS-232 Compact Fieldpoint controller and connect to it an RS-232 <-> RS-485 converter. Jbus communication functions are programmed into the controller based on the Modbus protocol that is compatible for our use. An Ethernet 8 relays card is added to increase the number of relays.
Also shown on the right side doors of the two cold rooms.
Software
- LabVIEW for programming and compiling the program embedded in the controller Compact Filedpoint
- LabVIEW RT Module for programming in LabVIEW embedded targets with real-time constraints
- Operating system of the Compact Fieldpoint controller: Phar Lap ETS IntervalZero (Group Citrix)
- HTTP server embedded in the Compact Fieldpoint controller to display directly in a web browser (Firefox, Internet Explorer …) the GUI controls and graphs
- FTP server embedded in the Compact Fieldpoint controller to download the executable and configuration files and data
You can access this interface from the Internet via a web browser like Google Chrome here.
How does it work?
The user has the option to choose, by a switch, using the bench in local mode with the classical control panel or using it in remote mode for examination and regulation by the Compact Fieldpoint. If the remote mode is selected, it is possible to visualize all the features, curves and calculations (entropy, enthalpy, Mollier diagram, performance coefficients) by connecting, via a web browser, to the controller. An LED lights when a remote user requests the control to change temperature settings or sending commands. A function allows the measurements recording for export to Excel. It is thus possible to reload these recordings to simulate the cooling system without making it work. Can be viewed simultaneously from multiple remote station but only one can get the control of the bench.