First International Conference on Energy Systems Engineering February 2-5, 2017 KBU—Karabuk, Turkey
Numerical and Experimental Comparison of Thermal Behaviors and Performances of The Monoblock Heat Exchanger Produced By Laser Sintering Method and Brazed Plate Heat Exchanger OsmanIPEK*,Mehmet KAN*+, BarışGUREL* Department of Mechanical Engineering, SüleymanDemirel University, Isparta, TURKEY
*
+
[email protected]
Abstract—Laser sintering technology(LST), which has been widely used recently, is a very important method to produce precise and qualified parts which cannot be manufactured with conventional methods. In this paper, the thermal behaviors and heat transfer performances of brazed plate heat exchanger (BPHE) and monoblock heat exchanger (MBHE) produced by laser sintering method from the AISI 316 stainless steel powder are numerically analyzed and experimentally investigated in an experiment setup. In analyzes, the inlet temperatures and mass flow rates of the hot and cold water are 𝐓𝐡𝐨𝐭 = 𝟔𝟎 𝐨 𝐂 , 𝐓𝐜𝐨𝐥𝐝 = 𝟏𝟓 𝐨 𝐂 and 𝐦𝐡𝐨𝐭 = 𝟎. 𝟐 𝐤𝐠/𝐬 , 𝐦𝐜𝐨𝐥𝐝 = 𝟎. 𝟏𝟏 𝐤/𝐬, respectively . According to analysis results; outlet temperatures of cold and hot fluids circulated in MBHE are 𝐓𝐜𝐨𝐥𝐝 = 𝟑𝟓. 𝟑𝟖 𝐨 𝐂, 𝐓𝐡𝐨𝐭 = 𝟒𝟖. 𝟐𝟒 𝐨 𝐂, respectively, while that in BPHE are 𝐓𝐜𝐨𝐥𝐝 = 𝟐𝟖. 𝟖 𝐨 𝐂 and𝐓𝐡𝐨𝐭 = 𝟓𝟐. 𝟒𝟎 𝐨 𝐂. According to experimental results, outlet temperatures of cold and hot fluids in MBHE were measured as𝐓𝐜𝐨𝐥𝐝 = 𝟑𝟓. 𝟕𝟐 𝐨 𝐂 , 𝐓𝐡𝐨𝐭 = 𝟒𝟖. 𝟓𝟎 𝐨 𝐂, respectively. As results of numerical and experimental analysis, heat transfer performance of the MBHE is 47.7% higher than BPHE, while its volume is 44.39% less. By comparing the results obtained from numerical and experimental analysis, it is observed that the results are consistent with each other.
increase the surface area.At the same time, both projecting and the porous surface are a combination of two successful applications in the manufacturing [2]. A review of studies in the literature; LST, which has been widely used recently, is a very important method to produce precise and qualified parts which cannot be manufactured with conventional methods.It has been observed that by using the LST method in the production of compact heat exchangers, it is possible to produce a low volume, high performance heat exchanger with much more complicated geometries.In addition, the roughness coefficient was investigated to investigate the thermal behavior.[3],[4],[5],[6],[7],[8]. They investigated the performance of the heat exchanger by using different fluids in the heat exchangers. Based on the cooling process and the temperature difference changes, correlations of condensation and flow boiling temperatures are derived. [9],[10],[11],[12],[13].
I. INTRODUCTION Heat exchangers are one of the most important and most common uses of engineering applications. Plate heat exchangers which take up little space, provide high heat transfer at high pressure drop. [1].
Thermal and dynamic analysis studies on CFD programmed plate heat exchangers in the literature have been studied. Numerical and analytical studies on plate heat exchanger heat transfer amount and effectiveness calculations and studies belonging to the methods used have been investigated. They observed the effect of heat transfer of different channel distances and surface area.Important parameters such as heat transfer coefficient, Reynolds number and Nusselt number have been studied and considered in heat exchanger designs.[14],[15],[16],[17],[18],[19].
Increasing the area of heat exchangers has a direct effect on the amount of heat transferred, so it is increasingly necessary to use heat exchangers with narrower volumes and larger surface area.Using porous surfaces or creating protrusions on the surface of the heat exchanger are the main methods to
In this paper, the thermal behaviors and heat transfer performances of BPHE and MBHE produced by laser sintering method from the AISI 316 stainless steel powder are numerically analyzed and experimentally investigated in an experiment setup.In the scope of the study, numerical analyzes
Keywords—Brazed Heat Exchangers, Monoblock Exchangers, Laser Sintering, CFD Analyzes
Heat
First International Conference on Energy Systems Engineering February 2-5, 2017 KBU—Karabuk, Turkey
of MBHE were made by designing with BPHE and the thermal behaviors of heat exchangers in different fluid flows were investigated.According to numerical results, experimental and numerical results were compared by performing experimental analysis of MBHE produced by LTS method. Unlike other works, the fin design on the MBHE layers and all the heat exchanger details are originally designed. The CFD analyzes were based on all of the heat exchangers, not locally, in BPHE and MBHE. It is possible to produce monoblock heat exchanger geometries which cannot be produced by other methods by LTS method. II.
NUMERICAL AND EXPERIMENTAL ANALYSES
A. Heat Exchangers Geometric Properties and Boundary Conditions The geometrical properties of BPHE and MBHE are given in Table 1. As shown in Fig.1, the geometry of the BPHE is designed and detailed in the 3-D CAD program.MBHE is designed and detailed in 3-D CAD program as shown in Fig. 2. Fig. 1 BPHESection View Drawings
Heat transfer of the heat exchangers between the channels and the channel walls are calculated. The roughness value of the BPHE in the channels and fins was 0.4 μm, while the roughness values in the MBHE produced by the LST method were taken as 40 μm.In analyzes, the inlet temperatures and mass flow rates of the hot and cold water are Thot = 60 o C , Tcold = 15 o C and mhot = 0.2 kg/s , mcold = 0.11 k/ srespectively. TABLE I THE GEOMETRIC PROPERTIES OF THE BRAZED PLATE HEAT EXCHANGER AND ORIGINAL COMPACT HEAT EXCHANGER
Thelength of theheatexchanger(mm) Thewidth of thecompactheatexchanger(mm) Hot water inletoutletpipediameter(mm) Coldwater inletoutletpipediameter(mm)
BPHE 192 74
MBHE 196 74
18
10
13
10
Fig. 2 MBHESection View Drawings
B. Numerical Analysis In the study, the boundary conditions used in the numerical analyzes are given in Table 2, while the experimental analysis of MBHE was carried out under the same boundary conditions.
First International Conference on Energy Systems Engineering February 2-5, 2017 KBU—Karabuk, Turkey
The material of BPHE is stainless steel and the solder material is copper. MBHE's material is stainless steel. TABLE II BOUNDARY CONDITIONS IN NUMERICAL AND EXPERIMENTAL ANALYSIS
Hot Water Inlet Temperature(C) Cold Water Inlet Temperature(C) Ambient Temperature(C) Hot Inlet Mass Flow Rate (kg/s) Cold Inlet Mass Flow Rate (kg/s)
60 15 27 0,2 0.11
TABLE III PARAMETERS USED IN ANSYS - FLUENT SOFTWARE
Wall-Turbulence Interaction Speed-Pressure Interaction Deconstruction Method Pressure, Momentum and Energy Equations Turbulence Kinetic Energy and Turbulence Distribution Ratio Used Thermal Properties of Materials Fluid Properties(Water) Plate Material GP1 (AISI 316, Stainless Steel Powder) Properties of Solder Material (Copper)
The most suitable parameter for comparisons of heat exchangers with each other is heat exchanger effectiveness. This can be written as follows in Eq. (2) [1]: Ɛ=
As shown in Table 3, properties of stainless steel and solder materials, methods used in numerical analysis, properties of water, plate material and solder material are given.
Simulation Condition Solver Type Viscous Model
Q = Heat that passed from heat exchanger (W) = Heat from the cooling hot fluid cools = Heat that warms the cold fluid
Steady-state Pressure Based Standard k − turbulence model Standard wall -function
T hg − T hç
=
T hg − T cç
C c (t cç − t cg )
(2)
C h (t hg − t cç )
D. ANSYS-FLUENT Basic Equation and Methods of Analysis Used in Analysis Software Based on the ANSYS-FLUENT finite volume method (other modeling programs can be used). The mesh file is limited by the program boundary conditions and parameters are selected by applying a solution for the system. Working in the background, the ANSYS-FLUENT program delivers a system solution using the equations that follow. The numerical analysis works in three-dimensions, uses conservation of mass and is assumed to be time independent to solve the momentum and energy equations [21]. Continuity Equation, as shown in Eq. (3) below: ∂(ρu)
SIMPLE Algorithm
∂x
Second Grade Center Difference Method Second Grade Center Difference Method Second Grade Center Difference Method
+
∂(ρv) ∂y
+
∂(ρw ) ∂z
=0
(3)
Conservation of Momentum Equation, as shown in Eq. (4), Eq. (5) and Eq. (6) below:
ρ (kg/m3) 998.2 8030
Cp (j/kgK) 4182 502.48
λ (W/m K) 0.6 381
8978
381
387.6
u
∂(ρu)
u
∂(ρu)
u
∂(ρu)
∂x
∂x
∂x
+v
∂(ρv)
+v
∂(ρv)
+v
∂(ρv)
∂y
∂y
∂y
+w
∂(ρw)
+w
∂(ρw)
+w
∂(ρw)
∂z
∂z
∂z
= −
∂P
= −
∂P
= −
∂P
∂x
∂y
∂z
+ μ
∂2 u
+
∂x 2 ∂2v
+ μ[
+
∂x 2
+ μ
∂2 w ∂x 2
+
∂2 u
∂2 v ∂y 2
∂2 u
+
∂y 2
∂z 2 ∂2 v
+
∂2 w ∂y 2
∂z 2
+
]
∂2 w ∂z 2
(4) (5) (6)
Conservation of Energy Equation, as shown in Eq. (7) below: u
∂(ρT) ∂x
+v
∂(ρT) ∂y
+w
∂(ρT) ∂z
= −
∂P ∂x
+
μ ∂2 T T ∂x 2
+
∂2 T ∂y 2
+
∂2 T ∂z 2
(7)
E. Experimental Analysis C. Heat Exchangers Thermodynamic Analysis Heat transfer in a heat exchanger, which is only between fluids and where it is accepted that there is no heat loss to the environment, can be calculated with Eq. (1) [1]: Q = k A ∆Tm According to this;
(1)
The heat exchanger experimental test set schematic diagram are given in Fig.6. As it can be shown Fig. 6, heat exchanger experimental test set include hot and cold water tanks, hot and cold water pumps, expansion tank, chiller, thermocouples, differential manometers, pipes and PLC automation system. In addition, images of BPHE and MBHE are shown in Fig. 7.
First International Conference on Energy Systems Engineering February 2-5, 2017 KBU—Karabuk, Turkey
Fig. 6 The heat exchanger experimental test set schematic diagram
In Figure 6, F, P, T and V represent flowmeter, manometer, thermocouple and valve, respectively.
Fig. 8 Temperature contour according to the CFD analysis result of BPHE
Fig. 7 MBHE and BPHE images
III.
ANALYSIS RESULTS
The numerical analysis results are shown in Fig. 8-13. According to the analysis results; as shown in Fig. 8, outlet temperatures of cold and hot fluids circulated in MBHE are Tcold = 35.38 o C, Thot = 48.24 o C , respectively, while that in BPHE are Tcold = 28.8 o C and Thot = 52.40 o C as shown in Fig. 9. According to experimental results, outlet temperatures of cold and hot fluids in MBHE were measured asTcold = 35.72 o C ,Thot = 48.50 o C respectively.As seen in Fig.10, the pressure drop on the cold fluid side is 682.3 Pa in the BPHE, while the pressure drop on the hot side is 818.3 Pa.As shown in Fig. 11, the MBHE also has a pressure drop of 6,344 Pa on the cold fluid side and 13,932 Pa on the hot fluid side.As shown in Fig. 12, the BPHE has a cold fluid inlet velocity of 0.83 m / s and a hot fluid inlet velocity of 0.78 m / s. In Fig. 13, the MBHE has a cold fluid exit velocity of 0.94 m / s and a hot fluid exit velocity of 0.99 m / s.
Fig. 9 Temperature contour according to the CFD analysis result ofMBHE
Fig. 10Pressure contour according to the CFD analysis result of BPHE
First International Conference on Energy Systems Engineering February 2-5, 2017 KBU—Karabuk, Turkey
channel geometry profile. Therefore, designing new original can be reduce occupied volume of heat exchanger and can be increase of the heat transfer amount and effectiveness of the heat exchanger. ACKNOWLEDGMENT This Research is supported by Turkish Scientific And Research Council(TÜBİTAK-1001) with project that project number is 214M070. REFERENCES [1]
Fig. 11Pressure contour according to the CFD analysis result of MBHE
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Fig. 12Velocity contour according to the CFD analysis result of BPHE
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[11] Fig. 13Velocity contour according to the CFD analysis result of MBHE [12]
IV.
CONCLUSIONS
As results of numerical and experimental analysis, heat transfer performance of the MBHE is 47.7% higher than BPHE, while its volume is 44.39% less. By comparing the results obtained from numerical and experimental analysis, it is observed that the results are consistent with each other.In the next studies, MBHE design can be improve and, pressure decreasing in the MBHE is reduce with designing new
[13]
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