Performance Analysis Of Heat Exchanger Research Articles

Thermal performance analysis of heat exchanger for closed wet cooling tower using heat and mass transfer analogy

In closed wet cooling towers, the heat transfer between the air and external tube surfaces can be composed of the sensible heat transfer and the latent heat transfer. The heat transfer coefficient can be obtained from the equation for external heat transfer of tube banks. According to experimental data, the mass transfer coefficient was affected by the air velocity and spray water flow rate. This study provides the correlation equation for mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental data. The results from this correlation equation showed fairly good agreement with experimental data. The cooling capacity and thermal efficiency of the closed wet cooling tower were calculated from the correlation equation to analyze the performance of heat exchanger for the tower.

Performance analysis of heat exchangers of an existing naphtha hydrotreating plant: A case study

This paper presents the performance evaluation of heat exchangers of an existing naphtha hydrotreating (NHT) plant. Originally, the NHT plant consisted of six plain tube heat exchangers connected in series. During plant revamps operation, three plain tubes were replaced with the three twisted tube heat exchangers. In this study, the heat exchangers data were collected from the plant before and after installation of the three twisted tube heat exchangers. The data were then analyzed to see the effects of the twisted tube configuration on fouling of heat exchangers and heat transfer. The analysis of the data showed that the twisted tube heat exchangers caused reduction in fouling resistance of tubes and increased the heat transfer. Also, the replacement of the three shells and tube type heat exchangers by the twisted tubes resulted in an increase of feed flow rate by about 7.85%. An economic analysis showed that the simple payback period for the twisted tube heat exchangers is 2.12 years. It can be concluded that considerable benefits in terms of energy and cost savings can be realized through the application of this innovative twisted tube heat exchanger technology in existing or new chemical plants.

A generalised mean temperature difference method for thermal design of heat exchangers

A Generalised Mean Temperature Difference (GMTD) method instead of the Logarithmic Mean Temperature Difference (LMTD) method for heat exchangers is proposed. Unlike the LMTD method, the GMTD method allows the performance analysis of heat exchangers with distributed physical properties. GMTD is calculated by a new method to take fluid temperature profiles as a function of heat load. Mathematical proof is made that the formula of the LMTD can be derived from that of the GMTD, in the case of constant physical property. The GMTD method is applied to experiments of a hot water supplier with supercritical carbon dioxide as a heating media that works through its pseudo-critical point where specific heat behaves anomalously. The empirical correlations of the local Nusselt number and pressure loss coefficient based on the GMTD gives an accurate prediction of the overall heat transfer coefficient, with a 5% error rating, whilst an error two times larger appears in the case of the LMTD.

Generalization of Logarithmic Mean Temperature Difference Method for Heat Exchanger Performance Analysis

Generalization of Logarithmic Mean Temperature Difference Method for Heat Exchanger Performance Analysis

Parametric Study of Radiative Heat Transfer in Arrays of Fixed Discrete Surfaces

The parameter space for study of radiative transfer in and through arrays of regular elements is extremely large. The present study has developed a number of correlations, based on MCLITE code results for simple geometric elements. These correlations can guide a designer of heat exchangers in optimizing performance. When the incident radiation is diffuse, these correlations are fairly accurate. When the incident radiation is collimated, and strikes the array at some arbitrary angle, the correlations are less accurate. For detailed analysis of heat exchanger performance there is no substitute for exercising a code such as MCLITE. 4 refs., 3 figs., 3 tabs.

Rotary Heat Exchangers With Time Varying or Nonuniform Inlet Temperatures

The performance of a counterflow, rotary heat exchanger operating with either transient or nonuniform inlet temperatures is investigated. The effect of transient inlet temperatures is analyzed in terms of the response of the outlet fluid temperatures to a step change in temperature of one of the inlet fluid streams. The effect of temperature nonuniformities is analyzed in terms of the change in steady-state effectiveness due to a circumferential temperature distribution in one of the inlet fluid streams. These temporal and spatial variations are explored using three different methods of analysis. An equilibrium analysis, assuming infinite heat transfer coefficients, is developed from kinematic wave theory. It is used to qualitatively describe the heat transfer process and define the upper limit of performance. A finite difference model of the governing differential equations, using finite transfer coefficients, is employed to obtain a detailed numerical analysis of heat exchanger performance. Results for the complete range of matrix to fluid capacity rate ratio are presented for a balanced and symmetric regenerator. At moderate capacity rate ratios, the numerical analysis predicts unusual temporal periodicity in the transient response. An experimental analysis has also been conducted using a counterflow, parallel passage, rotary heat exchanger made from polyester film. The results are used to substantiate predictions of the numerical model.