🚀 Heat Exchanger Calculator & Simulator
- Select Flow Configuration: Choose between Parallel Flow or Counter Flow configurations.
- Control Hot & Cold Fluid Inlet Temperatures: Input the hot fluid inlet temperature (Th,in) and cold fluid inlet temperature (Tc,in).
- Adjust Flow Rate & Heat Capacity Rate: Set the mass flow rate (m) and fluid type (water, oil, etc.) for both fluids to determine the heat capacity rate (C).
- Adjust Heat Transfer Area & Overall Heat Transfer Coefficient: Increase the heat transfer area (A) and overall heat transfer coefficient (U) to observe changes in thermal performance and LMTD.
📚 View LMTD and ε-NTU Heat Exchanger Calculation Theory & Guide ▼
1. Working Principle of Double-Pipe Heat Exchangers
A heat exchanger is a device designed to transfer thermal energy between two or more fluids of different temperatures without them directly mixing, separated by a solid wall. Among these, the double-pipe heat exchanger is the simplest and most fundamental type, consisting of one pipe positioned concentrically inside another, allowing fluids to flow through the inner pipe and the outer annular space (annulus) respectively.
- Parallel Flow: An arrangement where both fluids flow in the same direction (from left to right). It has a physical limitation: no matter how much the heat transfer area is increased, the outlet temperature of the hot fluid cannot drop below the outlet temperature of the cold fluid.
- Counter Flow: An arrangement where the two fluids flow in opposite directions. This configuration maintains a more uniform temperature difference throughout the exchanger, resulting in significantly higher heat transfer efficiency and the unique advantage of allowing the outlet temperature of the cold fluid to exceed that of the hot fluid.
2. Governing Equations: LMTD (Log Mean Temperature Difference) & ε-NTU Methods
The LMTD method and the effectiveness-NTU (ε-NTU) method are widely used for heat exchanger design and performance prediction.
① Total Heat Transfer Rate Formula:
q = U × A × LMTD [W]
Where U is the overall heat transfer coefficient (W/m²·K), A is the heat transfer area (m²), and LMTD is the Log Mean Temperature Difference defined by the following equation:
LMTD = (ΔT1 - ΔT2) / ln(ΔT1 / ΔT2) [°C]
- Counter Flow: ΔT1 = T_h,in - T_c,out , ΔT2 = T_h,out - T_c,in
- Parallel Flow: ΔT1 = T_h,in - T_c,in , ΔT2 = T_h,out - T_c,out
② ε-NTU Method (Useful when outlet temperatures are unknown):
Of the heat capacity rates C_h = m_h × cp_h and C_c = m_c × cp_c, the smaller value is designated as C_min and the larger as C_max. The maximum possible heat transfer rate is q_max = C_min × (T_h,in - T_c,in), and the actual heat transfer rate is determined by multiplying it by the effectiveness ε (q = ε × q_max).
NTU = U × A / C_min
The effectiveness ε is analytically derived as a function of the flow configuration and the capacity ratio C_r = C_min / C_max.
3. Engineering Significance of the Overall Heat Transfer Coefficient (U-Value)
The overall heat transfer coefficient U represents the total rate of heat transfer through the tube wall, combining inner wall convection, tube wall conduction, outer wall convection, and fouling resistance. For double-pipe configurations where the inner and outer surface areas are approximately equal, it is expressed as the sum of thermal resistances in series:
1/U ≈ 1/h_in + t/k_tube + 1/h_out
Consequently, even if a fluid with a high convective heat transfer coefficient (h), such as water, is used inside the tube, if the outer fluid is a poor heat transfer medium like gas or oil, the overall U-value will be limited to the level of the lowest convection coefficient due to this bottleneck. Using this simulator, you can conduct low-efficiency performance testing mimicking gas and oil environments.