Mixing Tee efficiency
Project By: Mayank Raj
ME Design eng. BITS Pilani
MIXING TEE EFFICIENCY
1. PROBLEM STATEMENT:
The job assigned here is to set up steady-state simulations to compare the mixing effectiveness in a Tee shape mixing CAD model when hot inlet temperature is 360C & the Cold inlet is at 190C. Using the k-epsilon and k-omega SST model for the first case and based on your judgment use the more suitable model for further cases. Giving the reason for choosing a suitable model is compulsory.
1.1 GIVEN DATA:
- Hot air inlet temperature = 36°c
- Cold air inlet temperature = 19°c
- Hot air inlet velocity = 3 m/s
- Momentum Ratio = 2 and 4 (Ratio of V(input) max and V(input)min
2.CAD MODEL AND GEOMETRY:
Fig: CAD solid model of the actual Tee shaped pipe with two inlets and outlet for mixing of two streams at different temperatures
2.2 VOLUME EXTRACTION:
The CFD of the hollow region is the actual region in which the hot and cold fluid flow analysis can be done. Thus the solid model shown below is the actual volumetric region through which the fluid flows and which actually needs to be meshed and analysed for its temperature and velocity profiles at various regions.
2.3 MESHING DETAILS:
Fig: 3D meshing of the volume extracted material in ANSYS mesh
Fig: The sectional trapezoidal elemental face version of the meshing showing the better view of the 3D volumetric meshing of the cad model
The meshing done after the naming of the different parameters shows the specifications of the volumetric mesh done by showing the number of nodes, elements and faces of the whole meshed component and its meshing quality which further decides the better resolution and preciseness of the solution calculations, the convergence of the residuals and the post analysis as well at last. Thus the very preciseness and more detailed result is much dependent on the meshing quality of the CAD model.
|
GEOMETRY |
SHORTER LENGTH MODEL |
LONGER LENGTH MODEL |
|
NUMBER OF NODES |
3142 |
3495 |
|
NUMBER OF ELEMNTS |
14247 |
15689 |
|
ELEMENT SIZE |
5 mm |
13.853 |
Table: Table for the comparison of the two different design meshing values and details.
The meshing details shown above in the table shows that even though the element size of the bigger CAD model is more than 2.5 times of the smaller model still the smaller model have comparable or almost same number of nodes and elements. This clearly depicts that when size of an element is reduced or increased how it drastically effects the number of elements and the nodes
2.4 MESHING QUALITY:
The below histogram shows he quality of mesh by comparing the elements metrics to the number of elements which shows the minimum % of elements with 28% element with the smallest number of element sizes with poor quality. This lowest % should be generally above 50% for the good meshing or around 40%.
Fig: Meshing quality of the shorter model
The min value for the element metrics for the short Tee is .28 and the max is 1as seen from the mesh quality histogram.
Fig: Meshing quality of the longer CAD model
The min value for the element metrics for the long Tee is .32 and the max is 1 as seen from the mesh quality histogram.
3. SETUP, DESCRETISATION, PHYSICS & MODEL:
3.1 SETUP:
Steady state pressure based absolute velocity formulation type solver is being used for both type of models so as per the same given conditions the comparison of the analysis can be further carried out. Energy has been included and considered for the solution part and a residual plot has been also plotted for various cases further.
3.2 DESCRETISATION:
Spatial discretisation has been carried out for the further solving of the problem using ANSYS fluent:
Gradient: Lest square cell based
Pressure: 2nd order
Momentum: 2nd order upwind
Turbulent kinetic energy: 2nd order upwind
Turbulent dissipations rate: 2nd order upwind
Energy: 2nd order upwind
3.3 PHYSICS & MODEL:
The comparative studies of two designs have been studied by the use of k-omega and k-epsilon model-epsilon model here used is the realizable with standard wall function for near wall treatment and SST k-omega model. Here Shear Stress Transport (SST) is a variant of standard k-omega model. SST is recommended generally for high accuracy boundary layer simulation.
3.3 MATERIAL:
Fig: Material used as a fluid for simulation
3.4 BOUNDARY CONDITIONS:
The given below boundary conditions are being used for calculation and simulation for both designs and the specific models as well.
|
BOUNDARIES |
VELOCITY |
TEMPERATURE |
|
INLET-X |
3 m/s |
36°C |
|
INLET-Y |
6m/s & 12m/s |
19°C |
|
OUTLET |
To be obtained as an output |
Room temp(26.5°C) |
Table: Boundary conditions table
4. RESULTS AND DISCUSSIONS (SHORT & LONG TEE MODEL) FOR TOTAL 8 CASES:
4.1 CASE 1: SHORT TEE GEOMETRY WITH MOMENTUM RATIO =2 USING K-epsilon MODEL
In this case shorter length Tee geometry was considered with a momentum ratio of 2 whereas temperature of inlet hot air was 36 °C with an incoming velocity of 3m/s. The temperature of cold inlet air was 19°C with an incoming velocity of 6m/s. the residual variables values are being shown on the plot below which shows how the residuals gets converged after certain iterations to give the stable value of temperature at outlet with the minimum standard deviation possible for comparative models.
Fig: Residual plot in case of short Tee for momentum ratio: 2 for K-epsilon Realizable Model.
As seen from the above plot we can say that the convergence started somewhere around the iterations of 500 and after that there is very negligible changes in the residual values w.r.t to the further iteration
The below fig shows the Area-weighted average for the temp outlet is around 30.2539°C and standard deviation is around 1.211075°C.
Fig: the area weighted average value of temperature and its standard deviation for the OUTLET
4.1.1 PLOTS:
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 500 iterations as per the plot below
Fig: The area-weighted average for temperature at outlet.
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 500 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. This is the plane that divides the geometry into two equal halves. The variation of temperature (user specified) and velocity (global) has been plotted.
Why global? The reason why the velocity isn’t user specified btw 3m/s -6m/s is that we also do need to know the stagnation points for the whole flow model here. The points where the velocity is almost zero or where there is no-slip condition.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region
Fig: Velocity variation in global reference in the plane region.
The region attracted to the wall or on the wall shows the region of almost no-slip condition and have almost zero velocity and comparatively very lesser temperature distribution or mixing takes place in this region. These regions can also be referred to as the stagnation points. This is why to study the nature of simulation the legend limits for the velocity profile has been set global and not user specified. If the limits for velocity would be set to user specified then that would not give us the exact region of the zero velocity profile area and thus no significant stagnation points would be clearly be achieved.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region
Fig: Velocity variation in global reference on a line across the section region
4.1.1.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines
4.2 CASE 2: SHORT TEE GEOMETRY WITH MOMENTUM RATIO =2 USING K-omega MODEL
In this case shorter length of geometry was considered with a momentum ratio of 2. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 6m/s. Fig. below shows the residual plot. The simulation was run for more than 1400 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 1100 iteration. It can be observed from residual plot, all parameters are converging its value after 1100 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 2 for K-omega, SST Model
4.2.1 PLOTS:
This model shows that it took much more number of iterations in this case to converge to the solution for the residuals as compared to the previous method. Area weighted temperature for output is 30.25°C
Fig: Area weighted average for temperature for the outlet.
Fig: Standard deviation of temperature at outlet with the number of iterations
Thus as seen from the area-weighted plot and standard deviation plot we can say that the deviation in the temperature for output is very large as compared to the previous model that was k-epsilon model.
Thus as per the plot and the time consumption the k-epsilon model seems to be more effective here for the momentum ratio of 2. Also the standard deviation for the model is around 2.01°C for the temperature at the outlet.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line accross the section region
Fig: Velocity variation in global reference on a line across the section region
4.2.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines
4.3. CASE 3: SHORT TEE GEOMETRY FOR MOMENTUM RATIO =4, USING K-epsilon MODEL
In this case shorter length of geometry was considered with a momentum ratio of 4. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 12 m/s. Fig. below shows the residual plot. The simulation was run for more than 500 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 200 iteration. It can be observed from residual plot, all parameters are converging its value from 200 to further iterations.
Fig: Residual plot in case of short Tee for momentum ratio: 4 for K-epsilon Realizable Model.
4.3.1 PLOTS:
This model shows that it took much lesser number of iterations in this case to converge to the solution for the residuals as compared to the previous boundary conditions. Area weighted temperature for output is 27.54°C and standard deviation is 1.37455°C.
Fig: Area weighted average for output temperature and its standard deviation
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 150-160 iterations as per the plot below
Fig: The area-weighted average for temperature at outlet
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 150 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line accross the section region
Fig: Velocity variation in global reference on a line across the section region
4.3.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines
CASE 4: SHORT TEE GEOMETRY WITH MOMENTUM RATIO =4, USING K-omega MODEL
In this case shorter length of geometry was considered with a momentum ratio of 4. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 12 m/s. Fig. below shows the residual plot. The simulation was run for more than 450 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 150 iteration. It can be observed from residual plot, all parameters are converging its value after 150 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 4 for K-omega SST Model.
4.4.1 PLOTS:
This model shows that it took much lesser number of iterations in this case to converge to the solution for the residuals as compared to the previous boundary conditions. Area weighted temperature for output is 27.57703 °C and standard deviation is 1.550874°C.
Fig: the area weighted average value of temperature and its standard deviation for the OUTLET
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 150 iterations as per the plot below
Fig: The area-weighted average for temperature at outlet
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable at 1.55 now onwards after around 150 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line across the section region
Fig: Velocity variation in global reference on a line across the section region
4.4.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines
Fig: Velocity variationin OUTPUT region on contours with the specific contours lines
CASE 5: LONG TEE GEOMETRY WITH MOMENTUM RATIO =2, USING K-epsilon MODEL:
In this case longer length of geometry was considered with a momentum ratio of 2. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 6 m/s. Fig. below shows the residual plot. The simulation was run for more than 300 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 200 + iteration. It can be observed from residual plot, all parameters are converging its value after 200 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 2 for K-epsilon Realizable Model.
4.5.1 PLOT:
Area weighted temperature for output is 30.2648 °C and standard deviation is 1.354 °C.
Fig: Area weighted average value of temperature and its standard deviation for the OUTLET
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 200 iterations as per the plot below.
Fig: The area-weighted average for temperature at outlet.
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 200 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations.
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region.
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region.
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line across the section region.
Fig: Velocity variation in global reference on a line across the section region.
4.5.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines.
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines.
CASE 6: LONG TEE GEOMETRY FOR MOMENTUM RATIO =2, USING K-omega SST MODEL
In this case longer length of geometry was considered with a momentum ratio of 2. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 6 m/s. Fig. below shows the residual plot. The simulation was run for more than 300 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 200 + iteration. It can be observed from residual plot, all parameters are converging its value after 200 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 2 for K-omega SST Model.
4.6.1 PLOTS:
Area weighted temperature for output is 30.32957 °C and standard deviation is 1.1510 °C.
Fig: Area weighted average value of temperature and its standard deviation for the OUTLET.
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 200 iterations as per the plot below.
Fig: The area-weighted average for temperature at outlet.
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 200 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations.
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region.
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region.
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line across the section region.
Fig: Velocity variation in global reference on a line across the section region.
4.6.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines.
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines.
CASE 7: LONG TEE GEOMETRY FOR MOMENTUM RATIO =4, USING K-epsilon MODEL
In this case longer length of geometry was considered with a momentum ratio of 4. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 12 m/s. Fig. below shows the residual plot. The simulation was run for more than 450 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 250 + iteration. It can be observed from residual plot, all parameters are converging its value after 250 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 4 for K-epsilon Realizable Model.
4.7.1 PLOTS:
Area weighted temperature for output is 27.48819 °C and standard deviation is 0.5737452 °C.
Fig: Area weighted average value of temperature and its standard deviation for the OUTLET.
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 200+ iterations as per the plot below.
Fig: The area-weighted average for temperature at outlet.
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 200 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations.
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region.
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region.
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a across the section region.
Fig: Velocity variation in global reference on a line across the section region.
4.7.2 CONTOURS:
Fig: Temperature variationin OUTPUT region on contours with the specific contours lines.
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines.
CASE 8: LONG TEE GEOMETRY FOR MOMENTUM RATIO =4, USING K-omega SST MODEL
In this case longer length of geometry was considered with a momentum ratio of 4. The temperature of inlet hot air was 36 degree-centigrade with an incoming velocity of 3m/s. The temperature of cold air was 19 deg C with an incoming velocity of 12 m/s. Fig. below shows the residual plot. The simulation was run for more than 600 time-step in order to confirm for convergence of simulation results. The simulation was converged after running it for 190 + iteration. It can be observed from residual plot, all parameters are converging its value after 190 iterations and further.
Fig: Residual plot in case of short Tee for momentum ratio: 2 for K- omega SST Model.
4.8.1 PLOTS:
Area weighted temperature for output is 27.48671 °C and standard deviation is 0.6379888 °C.
The below plots shows the area weighted average of the temperature at the outlet zone. This value basically shows the change in temperature w.r.t to the iterations which after converging after a certain point shows the outlet temperature goes stable now onwards after around 190 iterations as per the plot below
Fig: Area weighted average value of temperature and its standard deviation for the OUTLET.
Fig: The area-weighted average for temperature at outlet.
The below plots shows the standard deviation of the temperature at the outlet zone. This value basically shows the change in deviation of temperature w.r.t to the iterations which after converging after a certain point shows the outlet standard deviation of temperature goes stable now onwards after around 190 iterations as per the plot below.
Fig: Standard deviation of temperature at outlet with the number of iterations.
The following plots shows the variation of temperature and velocity on a plane generated between the geometry. The variation of temperature (user specified) and velocity (global) has been plotted.
Fig: Temperature variation from 19 deg C to 36 deg C in the plane region.
Fig: Velocity variation in global reference in the plane region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region.
Fig: Velocity variation in global reference on a line along the length region.
Fig: Temperature variation from 19 deg C to 36 deg C on a line along the length region.
Fig: Velocity variation in global reference on a line across the section region.
4.8.2 CONTOURS:
Fig: Temperature variation in OUTPUT region on contours with the specific contours lines.
Fig: Velocity variation in OUTPUT region on contours with the specific contours lines.
5. MESH INDEPENDENT STUDY:
5.1 MESH DETAILS COMPARISION:
AIM: To show that temperature at monitor point doesn’t depend on meshing of geometry.
Here to study the mesh independent study we will consider case 4 for K-omega SST model for short Tee design. Here model of shorter length with momentum ratio of 4 is given. The inlet velocity of hot air is 3 m/s & cold air is 12 m/s. The inlet temperature of hot air is 36 degree centigrade & cold air is 19 degree centigrade.
The variation of temperature and velocity by dependence on the quality of mesh for comparing on the basis of various parameters will be studied. The residual plots, area weightage average and standard deviation temperature will be one of the parameter for this comparative observation for different meshing size and quality.
|
MESHING DETAILS |
CASE 1 (0.01m) |
CASE 1 (0.005m) |
|
NUMBER OF NODES |
2797 |
3142 |
|
NUMBER OF ELEMENTS |
12583 |
14247 |
|
ELEMENT SIZE |
0.01m |
0.005m |
Element size when was decreased from 10 mm to 5 mm. The number of nodes increased from 2797 to 3142. There was also increase in number of elements from 12583 to 14247.
Fig: Meshing of the sectional view with tetrahedral faces for 0.01 m Element size
The elements in the below figure with 0.005m element size do look smaller in size compared to the elements of the previous fig with meshing size 0.01.
Fig: Meshing of the sectional view with tetrahedral faces for 0.005 m Element size
5.2 RESIDUE VARIABLES COMPARISION:
Below shown values of all residual variables on the plot for k-omega SST model for the elemental mesh size of 0.01m. The plot converges here after the 800+ iterations here given that the mesh size was very large comparatively for this case.
Fig: Residual plot for the mesh size of 0.01m by k-omega SST model.
Fig: Residual pot converges more quickly here for 0.005m as compared to the bigger mesh size
Thus the number of iterations taken in the case of finer mesh is lesser as seen from the residual plots.
Area weighted average for the outlet temperature is being listed here by the plot below which is 27.55 deg C
This value for the below plot is very much similar to and almost same as the value of the other comparison case which is for 0.005m. This shows that the area weighted average temperature in both the cases are almost same.
Fig: Area weighted average for outlet temperature
Also in the case of the standard deviation the value as per the below plot is 1.2572 deg C which was 1.55 deg C in the case of 0.05m mesh case which is very much near
Fig: Standard deviation for the temperature at outlet for the meshing size of 0.01m
Thus it can be concluded from the comparison of plots that there is exact same outlet temperature as per the area weighted average and for standard deviation of temperature for outlet case too there is very slight change in the value of around 0.293 deg C.
This shows that even for the difference of almost twice element size there is very slight or almost no change in the outlet temperature and deviation in the temperature which do shows the mesh independency criterion and only change is the computational time for the running of simulation.
6. CONCLUSION:
6.1 COMPARAISION OF OUTLET TEMPERATURE FOR ALL THE CASES:
|
CASES |
INLET VELOCITY ( m/s) |
GEOMETRY TYPE |
TEMPERATURE AT OUTLET(°C) |
STANDERD DEVIATION OF TEMPERATURE |
|
|
HOT AIR |
COLD AIR |
||||
|
CASE 1 |
3 |
6 |
SHORT TEE |
30.2539°C |
1.211075°C |
|
CASE 2 |
3 |
6 |
SHORT TEE |
30.25°C |
2.01°C |
|
CASE 3 |
3 |
12 |
SHORT TEE |
27.54°C |
1.37455°C. |
|
CASE 4 |
3 |
12 |
SHORT TEE |
27.57703 °C |
1.550874°C |
|
CASE 5 |
3 |
6 |
LONG TEE |
30.2648 °C |
1.354 °C. |
|
CASE 6 |
3 |
6 |
LONG TEE |
30.32957 °C |
1.1510 °C. |
|
CASE 7 |
3 |
12 |
LONG TEE |
27.48819 °C |
0.5737452 °C |
|
CASE 8 |
3 |
12 |
LONG TEE |
27.48671 °C |
0.6379888 °C |
Seeing the above data we can say that whether it be case of short or long geometry the velocity of inlet air plays a very big role in the outlet temperature.
The cases in which the minimum temperature inlet has the velocity of 12 m/s is the case where the temperature of inlet is around 27.5 deg C around.
Also the standard deviation in the case of longer geometry in case of momentum ratio 4 the outlet temperature is very less as compared to the rest cases. Thus apart from the cases of momentum ratio being 4 having greater efficiency we can say that the case for the longer geometry where the momentum ratio is 4 both the k-epsilon and K-omega SST model are very much effective and requires the lesser computational details for the calculations and convergence of the solution.
Also the case where the geometry is shorter and with momentum ratio of 2 is the case where the standard deviation is maximum is the case which is much lesser effective than the other cases.
Thus seeing the data of results we can conclude that specifically velocity of the cooler inlet air or the momentum ratio of greater magnitude alone plays a very big role in the total resultant temperature which particularly shows the minimum deviation in the results in the case 7 & case 8 which shows the effectiveness of the results and a justified simulated comparison.