User interface design considerations EESCoolTools - a collection of simulation models for refrigeration applications

When designing a user interface for a simulation model there are several important issues to consider: Who is the target user group, and which a priori information can be expected. What questions do the users want answers to and what questions are answered using a specific model? When developing the user interface of EESCoolTools these issues led to a series of simulation tools each with a specific purpose and a carefully selected set of input and output variables. To allow a more wide range of questions to be answered by the same model, the user can change between different sets of input and output variables. This feature requires special attention when designing the user interface and a special approach for controlling the user selection of input and output variables are developed. To obtain a consistent system description the different input variables are grouped corresponding to the phenomena they describe and the user can select only one input variable per phenomena. This method ensures that all phenomena are described i.e. the equation system is non singular. Numerical robustness of the model is assured by applying a so-called cycle-cored numerical structure, which has the consequens that the user does not have to specify any start guesses, etc. The design approach developed have resulted in a number of simulation tools which allow users with limited theoretical knowledge about refrigeration systems, mathematical models and simulation to use them while the expert users still have a lot of flexibility in choosing input variables and in assigning values of parameters. Background EESCoolTools [1] is a selection of simulation tools aimed at the refrigeration industry. Today, a lot of people do not use any kind of simulation tools when designing or modifying refrigeration systems. They rely on rules of thumb and the use of component selection tools from the different manufactures. To design more energy efficient refrigeration systems energy consultants and engineers could benefit from using simulation tools. The name EESCoolTools is a combination of the three words EES, Cool and Tools: • "EES" refers to the name of the program used to develop the simulation models (Engineering Equation Solver EES) by FChart [2]. • "Cool" refers to that the programs are related to the area of refrigeration. • "Tools" refers to that the programs are thought to be tools enabling you to make faster and more detailed system design and energy analysis. EESCoolTools is a part of the software collection CoolPack [1], [4]. The design goal of EESCoolTools has been to develop simulation tools that are easy and fast to use. The users should not encounter any numerical problems. This has demanded careful attention on both the numerical parts of the tools and the user interface. The easy way to make a simulation tool numerically robust is to limit the freedom of the user. This could be to limit the number of inputs to the model or to use a single input output structure. But this is not a very satisfying way of solving the problem as it constrains the use of the simulation model