U型翅片管换热器传热单元数计算式

Approximate formulas of number of transfer unit of U shaped fintube heat exchangers

摘要:

为了得到U型翅片管换热器传热单元数计算式,以U型翅片管换热器为研究对象,通过建立翅片管换热模型,推导出了逆流和顺流2种流体流动趋势的传热单元数计算式(NTU计算式)．分别采用推导出的传热单元数计算式(εNTU法)和前人推导出的平均温差关系式(LMTD法)计算U型翅片管传热系数,并进行对比分析．结果表明,当进水温度为45～60 ℃,热水流量为30～110 kg／h时,由εNTU法和LMTD法计算出来的翅片管传热系数相差很小．所推导出来的U型翅片管换热器传热单元数计算式是合理的．

Abstract:

To obtain the formulas of number of transfer unit (NTU) of U shaped fintube heat exchangers, a U shaped fintube heat exchanger is taked as research object. Approximate NTU formulas of number of transfer unit are derived by establishing heat transfer model of U shaped fintube when the trend of two flows in fintube heat exchanger is counter and parallel, respectively. Subsequently, the heat transfer coefficients of fintube are compared and analyzed by effectivenessnumber of transfer unit method (εNTU method) and logarithm mean temperature difference method (LMTD method) when inlet water temperature is from 45 ℃ to 60 ℃ and water flow rate is from 30 kg／h to 110 kg／h. The results show that, the difference of the heat transfer coefficients respectively calculated by εNTU method and LMTD method is so small that these NTU formulas are valid