Algorithm for Program of the Vertical Thermosiphon Re-boiler

Paper will present algorithm for program and estimation of the vertical thermo-siphon re-boiler, using the FORTRAN77 programming language that is based on the method of Sarm and al. Unlike previously proposed approaches and the literature this method in the estimation of the pressure drop in pipes apparatus, takes into account the mechanism of the two-phase ow. The results of the program are analyzed in detail and discussed in the exploitation of real examples. presents the algorithm and results of programs written in FORTRAN77 programming language for the design of vertical thermo-siphon re-boilers with boiling in the block and a set of model equations for of which are taken from the it was establish on the example of boiling in a wider range of process (heat transfer, vapor phase composition at exit


Introduction
Paper presents the algorithm and results of programs written in FORTRAN77 programming language for the design of vertical thermo-siphon re-boilers with boiling in pipes. Thus, starting from the block diagram and a set of model equations for the calculation of pressure drop and heat transfer, which are taken from the literature [1], it was necessary to establish an appropriate algorithm. Written program has been tested on the example of boiling propane in a wider range of process conditions (heat transfer, vapor phase composition at the exit of the device) as well as a series of geometric characteristics of the device (pipe diameters and lengths).

Methods
Several methods of analysis are available, but one of the rst who published works on this topic were Fair [6] and Hughmark [7,8,9,10]. Fair's method provides procedures for the calculation of pressure drop and heat transfer along the entire pipe exchangers, using the increment of the proportion of the gas phase and the correlation developed by Lochart-Martinelli [11] for two-phase ow. The method includes the calculation of proportion and errors using a series of diagrams. Using Lochard-Marinelli parameter Fair thus does not introduce the factor that would accurately encompass vertical ow so Davids proposed Froude number thus modi ed the previous method. The correlation for the calculation of uid retention is given in the expression of Lochard-Mrtinelli parameter, and is valid for the mass ux greater or equal to 567 kW/m2. For the mass ux less than 567 kW/m2 deviation of the Lochard-Martinelli parameter is a function of the total mass velocity. This method represents the isothermal conditions in the pipe exchangers and constant difference between the temperature of the pipe wall and the uid. Correlation for calculating the coe cients of the transfer of the boiling heat is Hughmark's and is more or less similar to Fair's. Bankof's modi ed correlation was used to calculate the retention of uid and gas. Chensho's correlation [13] explains the effect of ow on the boiling rate/speed, and was used to calculate the hb coe cients. This correlation takes into account the changes in physical properties. The above method does not consider the different ow regimes for the calculation of pressure drop and heat transfer.
Calculation methods of the vertical thermo-siphone reboiler This method proposed by Sarma [1], is based on consideration of the two-phase ow regime during the calculation of the pressure drop and heat transfer coe cient. Calculation of heat transfer can be divided into estimating the nucleation boiling and convective heat transfer coe cient of notable heat zone and the two-phase region. The equations proposed by Orkizewski [4] for vertical two-phase ow are used in the proposed method. Orkizewski made an analysis of the results of Gri th, Wallis, Duns and Ross [2] pressure drop to their data bank of petrochemicals and selected the best models. Orkizewski developed relations for the pressure gradient, two-phase density and acceleration expression for a given ow regime (Table 1).

Results And Discussion
Algorithm results of examples reboilera propane column with different combinations of tube geometry, heat ux and inlet pressure drop. For a given heat ux and the geometry of the pipe; partition coe cient of heat transfer and pressure drop of uid tends to decrease with increasing inlet pressure drop. Reducing the speed Vl can be attributed to the reduction of the available pressure at the entrance to reboiler. From table for a certain pecking speed, increase speed Vl accompanied by a reduction in the share of the money. The coe cient of thermal transitions can show other variations.The in uence of the geometry of the pipe to uid retention along the entire length of the pipe shows the variation of heat transfer coe cient along the entire length of the pipe. In all cases, the piston area throughout the two-phase fault zone and is therefore approximate S shape..

Conclusions
The results are satisfactory agreement with the corresponding values from the literature [1]. Bearing in mind that the convergence criteria are input data to the calculation, as well as the fact that their values are not listed in the literature [1] in this paper the ranges of their numeric values are de ned by systematic usage of the software. All the data on distribution of heat ow, pressure drop, distribution of heat transfer coe cients and the proportion of gas and liquid phases by the height of pipe are shown in detail. Based on this, conclusions can be made about the length of each zone of the two-phase ow. The results from this study were compared with values from the literature [1] and by using the graphic way. This comparison shows that there are different degrees of matching results. Depending on the calculated value. One possible reason for obtaining a deviation could be attributed to possible errors in the model equations that could not be veri ed because of the unavailability of the literature. This possibility is pointed out by the facts that we have learned on a few incorrect model equations which will, luckily, be removed. In this sense, further work on this model could include a more detailed check of the model equations according to the original literature. The algorithm and the program that was used in this study provide a good basis for their further development in order to broaden the application of multi-component system (Fig. 1.)  The ratio of velocity VL ow and heat ux