Heat Transfer Numerical Simulation And Thermodynamic Study Of Compact Air-Cooled Condenser

Compact air-cooled condenser is a kind of plate-fin heat exchanger, the flow andheat transfer characteristics of the fin’s surface play a decisive role in the compactair-cooled condenser. In this paper, the study of compact air-cooled condenser is basedon the level of fin.The structure after welding plain-fin and partition is equivalent to installing anumber of rectangular fins on the partition.In this paper, the minimum entropy generationof the fin is studied. On the basis of several classic formulas and empirical formulas, withintegration and derivation,get all the formulas needed to calculate the minimum entropygeneration number of plain-fin and determine the range of variables. With the help ofMATLAB, we can obtain the relation curves between minimum entropy generationnumber N_Sand the Reynolds number corresponding fin length Re_Lin laminar orturbulent state, and try to analysis variation trend of Reynolds number corresponding theoptimum fin heightRe_b,opt. To transform two composite variables M and B, draw newrelation curves and discuss their influences to minimum entropy generation number.Inlaminar state, minimum entropy generation number N_Swill firstly decrease and thenremain unchanged with the increase of Re_L,in turbulent state, N_Swill increase veryquickly with the increase of Re_L; Whether in laminar or turbulent state,minimumentropy generation number N_Swill increase with the increase of M or B;Re_b,optwillchange with Re_Land finally remain unchanged,and the value ofRe_b,optin turbulentstate is far less than the value in laminar state.In this paper,the physical model is simplified,a symmetry cell of the cold air side isselected for study. The author uses the preprocessing software Gambit to set up modeland divide meshes,then uses Fluent for numerical simulation and analyze wind speed, fin height and fin spacing’s influences to the fin’s flow and heat transfercharacteristics.Along the flow direction，the air temperature gradually rises and speedincreases, resulting in pressure drop Pand the convective heat transfer coefficient hreduces gradually. when wind speed is larger, air temperature in each section is lower,and stable laminar boundary layer’s formation is later which is helpful for heat transfer,the convective heat transfer coefficient h and pressure drop Pare both larger; Whenfin height is lower, its influence to heat exchange is relatively small, the air temperaturein each section is a little higher and speed is slightly slower, h and AP are bothsmaller;When fin spacing is smaller, the air temperature in each section is much higher,and the boundary layer is thinner which is helpful for heat transfer.