1. A process simulation system including a processor and a memory coupled to the processor, the process simulation system being configured to cause the processor to execute a process simulation by simulating operations of various component elements constituting a production system so as to determine a process organization of the production system, comprising: an element arrangement data reading unit configured to sequentially read component element names which are combined with process identification names from an element arrangement data, the element arrangement data describing an arrangement of the various component elements constituting the production system with combinations of the process identification names and the component element names along a work flow; an element definition file reading unit configured to sequentially read element definition files corresponding to component element names which had been read in by the element arrangement data reading unit from a plurality of element definition files, the element definition files describing simulation programs for executing operational simulations of the various component elements for each of the component elements; a program array preparing unit configured to prepare a simulation program array by sequentially arranging simulation programs respectively described in element definition files which had been read in by the element definition file reading unit; and a program execution unit configured to simulate operations of the various component elements constituting the production system by executing a series of simulation programs included in the simulation program array prepared by the program array preparing unit, wherein the element arrangement data comprise tabular form data prepared using software capable of editing to add and delete textual information, the work flow being set in a row direction, and the process identification names and the component element names being described in a line direction, wherein each of the element definition files contains a program description describing an own simulation program and a variable description describing a variable used in the own simulation program, in the variable description, an external reference variable to designate a referring variable being defined in a case of an element definition file to refer to a variable in an other element definition file, and a take-out variable referred to by an external reference variable being defined in a case of an element definition file to make an other element definition file refer to a variable, the process simulation system further comprising: a variable array preparation unit configured to prepare a variable array including all variables described in the variable description of each of the element definition files which had been read by the element definition file reading unit; and a variable corresponding unit configured to make the external reference variable contained in the variable array prepared by the variable array preparation unit correspond to the take-out variable, wherein a variable name replacing data for replacing a variable name described in the variable description of each of the element definition files to a different variable name is described in the element arrangement data, and the process simulation system further comprising a variable name replacing unit configured to replace a variable name for which the variable name replacing data is set in the element arrangement data to an other variable name described in the variable name replacing data.