逆流换热器：T_h,in=100°C，T_h,out=60°C，T_c,in=20°C，T_c,out=50°C → ΔT₁=50 K，ΔT₂=40 K，LMTD≈44.81 K 逆流。ΔT₁=T_h,in-T_c,out=100-50=50 K，ΔT₂=T_h,out-T_c,in=60-20=40 K。LMTD=(50-40)/ln(50/40)=10/0.2231≈44.81 K（以代码为准）。{"result":"Heat exchanger LMTD (counter flow). T_h,in=100 °C, T_h,out=60 °C, T_c,in=20 °C, T_c,out=50 °C. ΔT₁=50 K, ΔT₂=40 K. LMTD = 44.8142 K.","metadata":{"input":{"flowType":"counter","hotInletTemp":100,"hotOutletTemp":60,"coldInletTemp":20,"coldOutletTemp":50,"tempUnit":"°C"},"result":{"lmtd_K":44.8142,"deltaT1_K":50,"deltaT2_K":40,"flowType":"counter","heatFlowRate_W":null,"overallHeatTransferCoeff":null,"area_m2":null}}}
顺流换热器（含 U、A）：T_h,in=120°C，T_h,out=70°C，T_c,in=30°C，T_c,out=60°C，U=500，A=2 m² → LMTD≈36.41 K，Q≈36409 W 顺流。ΔT₁=T_h,in-T_c,in=120-30=90 K，ΔT₂=T_h,out-T_c,out=70-60=10 K。LMTD=(90-10)/ln(90/10)=80/ln(9)≈36.41 K。Q=U·A·LMTD=500·2·36.41≈36409 W。{"result":"Heat exchanger LMTD (parallel flow). T_h,in=120 °C, T_h,out=70 °C, T_c,in=30 °C, T_c,out=60 °C. ΔT₁=90 K, ΔT₂=10 K. LMTD = 36.4096 K. Q = U·A·LMTD = 500 W/(m²·K) · 2 m² · 36.4096 K = 36409.5691 W.","metadata":{"input":{"flowType":"parallel","hotInletTemp":120,"hotOutletTemp":70,"coldInletTemp":30,"coldOutletTemp":60,"tempUnit":"°C","heatTransferCoeff":500,"area":2},"result":{"lmtd_K":36.4096,"deltaT1_K":90,"deltaT2_K":10,"flowType":"parallel","heatFlowRate_W":36409.5691,"overallHeatTransferCoeff":500,"area_m2":2}}}