H-type Finned Tube Research Articles

Heat transfer, erosion and acid condensation characteristics for novel H-type finned oval tube

Low efficiency of heat transfer, acid corrosion and erosion of economizers affect the economy and security in coal-fired power plants significantly. The H-type finned oval tube is proposed to alleviate these problems. Based on the H-type finned oval tube, we investigated three novel types of fins, including bleeding dimples, longitudinal vortex generators (LVGs), and compound dimple-LVG. We considered the three aspects together, and obtained the heat transfer, acid condensation rate and erosion loss. The results show that the tube bank with the new structured fins can improve the performance on the three aspects, and the compound dimple-LVG performs the highest comprehensive effect.

Experimental Investigation of Heat Transfer and Pressure Drop Characteristics of H-type Finned Tube Banks

H-type finned tube heat exchanger elements maintain a high capacity for heat transfer, possess superior self-cleaning properties and retain the ability to effect flue gas waste heat recovery in boiler renovations. In this paper, the heat transfer and pressure drop characteristics of H-type finned tube banks are studied via an experimental open high-temperature wind tunnel system. The effects of fin width, fin height, fin pitch and air velocity on fin efficiency, convective heat transfer coefficient, integrated heat transfer capacity and pressure drop are examined. The results indicate that as air velocity, fin height and fin width increase, fin efficiency decreases. Convective heat transfer coefficient is proportional to fin pitch, but inversely proportional to fin height and fin width. Integrated heat transfer capacity is related to fin efficiency, convective heat transfer coefficient and finned ratio. Pressure drop increases with the increase of fin height and fin width. Finally, predictive correlations of fin efficiency, Nusselt number and Euler Number are developed based on the experimental data.

Sulfuric acid deposition characteristics of H-type finned tube bank with 10 rows

Abstract The deposition rate and condensate mass fraction of sulfuric acid on heat exchanger surfaces play a decisive role on the local low-temperature corrosion of heat exchangers. Based on the prediction model of acid deposition, a three-dimensional numerical simulation was performed for acid deposition characteristics of H-type finned tube bank with 10 rows. The effect of six geometric parameters (spanwise tube pitch, longitudinal tube pitch, fin height, fin pitch, fin thickness and slit width) and Reynolds number are examined. It can be observed that the fin thickness and Reynolds number have the most significant effect on acid deposition. A large fin thickness will greatly increase the risks of fin corrosion, and it is not recommended for practical use. According to the calculation results, a correlation of Sh number of sulfuric acid vs fin geometries for the 10-row tube bundle is presented.

Numerical investigation of heat transfer and erosion characteristics for H-type finned oval tube with longitudinal vortex generators and dimples

To improve heat transfer performance and reduce erosion of economizers in coal-fired power plants, firstly the heat transfer and erosion characteristics is numerically studied for the single H-type finned oval tube with enhanced heat transfer structures including bleeding dimples, longitudinal vortex generators (LVGs), and compound dimple-LVG. The simulation results show that the oval tube with compound LVG-dimple achieves the highest overall heat transfer performance while the oval tube with LVG works most efficiently in the anti-wear performance. Then based on the H-type finned oval tube, the LVG structure on the first row of tubes together with hemisphere protrusions design, while the compound LVG-dimple on the rest tubes are also simulated. The optimized H-type finned oval tube bank heat exchanger is demonstrated of high performance on both heat transfer and anti-wear.

Study on Heat Transfer and Resistance Characteristics of H-Type Finned Tube

Three-dimensional numerical study is performed for heat transfer and resistance characteristics as well as comprehensive performance of two kinds H-type (single and double) finned tube. It is found that the heat transfer and resistance characteristics as well as comprehensive performance of H-type finned tube are influenced by the Reynolds number of gas. With the growth of Reynolds number, the air-side Nusselt number rises gradually and the heat transfer performance gets better and better, whereas the air-side Euler number drops step by step until close to a fixed value. The comprehensive performances of both single H-type finned tube and double ones are weaken progressively. When Reynolds number value is same, the convective heat transfer, pressure drop, air-side Nusselt number and Euler number of single H-type finned tube are bigger than those of double ones. The single H-type finned tube expression is much better than double ones in comprehensive performance and heat transfer.

A numerical study of the deposition characteristics of sulfuric acid vapor on heat exchanger surfaces

Accurate predictions of the sulfuric acid condensation behavior on the surfaces of heat exchangers are crucial for understanding the local low-temperature corrosion characteristics of heat exchangers and designing them. In this paper, a new numerical model has been developed to predict the condensation rate of sulfuric acid and condensate acidic solution concentration on heat exchanger surfaces. By correlating the vapor–liquid equilibrium (VLE) data of H2SO4–H2O solutions from experiments and in conjunction with multi-component diffusion theory, the proposed model obtains numerical solutions of condensation heat transfer under the conditions of a coupled wall and fluid boundary condition and a multi-component mixture of flue gas and the sulfuric acid solution (saturated partial pressure of sulfuric acid and water vapor). The numerical model has been validated by a comparison of the simulation results with available experimental data, and applied to an analysis of the H-type finned tube heat exchanger, which has been widely used in the field of waste heat recovery. The distributions of the condensation rate and condensate concentration on the fin surface are also calculated. The results show that the three dimensional distribution of acid solution concentration is consistent with the fin temperature. An increase in water vapor could result in a sharp reduction of the acid solution concentration and an increase in deposition, which may indicate a serious risk for low-temperature corrosion. In contrast, increasing the flue gas temperature will reduce the corrosion risk by reducing the condensation rate and increasing the acid concentration.

Parametric study and field synergy principle analysis of H-type finned tube bank with 10 rows

In this paper, three-dimensional numerical studies are performed for heat transfer and pressure drop characteristics of H-type finned tube bank with 10 rows by software FLUENT. The effects of seven geometric parameters (tube row number, fin thickness, slit width, fin height, fin pitch, spanwise tube pitch and longitudinal tube pitch) and Reynolds number are examined. It is found that for the tube bundle studied, the heat transfer and fluid flow are in the developing region, and they become periodically fully developed after the 10th row. Among the seven geometric parameters spanwise tube pitch has the most important effect and slit width has the least important effect, with other five parameters in between. The results are also analyzed from the view point of field synergy principle. It is found that the effects of the eight parameters on heat transfer and fluid flow characteristics can be well described by the field synergy principle. Correlations of Nu and Eu for the 10-row tube bundle are presented.