Varying Inlet Temperature Research Articles

Design and 3E analysis of a hybrid power plant integrated with a single-effect absorption chiller driven by a heliostat field: A case study for Doha, Qatar

This study suggests a novel zero-emission combined cooling and power (CCP) system using a high-temperature solar field, i.e., heliostat reflectors and a central receiver as the heat supplier of the whole system. In addition to the solar field, the proposed system consists of a hybrid power plant comprising a closed Brayton cycle using helium gas and a Kalina cycle, and a cooling production unit through a single-effect absorption chiller. To ameliorate the technical contribution of the current research work, the system suggested here was considered for a case study in Doha, Qatar. Hence, a comprehensive parametric analysis taking into account the energy, exergy, and exergoeconomic (3E analysis) performance criteria based on crucial design parameters is conducted. Furthermore, the economic feasibility analysis of the system is carried out through appraising the net present value. Regarding the parametric analysis, the 3E criteria evaluated here exhibited more sensitivity to variation in heliostat field efficiency and helium turbine inlet temperature, respectively. Moreover, the baseline design mode demonstrated that the electricity was produced by 15.29 MW, the coefficient of performance (COP) of the cooling production unit was 0.812, and also the overall exergy efficiency and sum unit cost of products were obtained as 29.87% and 4.34 $/GJ, respectively. Likewise, for the electrical unit exergy cost of 0.05 $/kWh and cooling unit exergy cost of 0.08 $/kWh, the calculated net present value and payback period of the suggested system were correspondingly equal to 1.605×107 and 3.1 years.

Field-scale experimental and numerical analysis of a downhole coaxial heat exchanger for geothermal energy production

The experimental and computational analyses of a 500 m deep coaxial borehole heat exchanger system for geothermal power generation are studied in this paper. The experiments are carried out on a high temperature resourced well with an average thermal gradient of 0.38 °C/m. The experiment lasts 456 h, and the findings are described in terms of fluid inlet and outlet temperatures, subsurface temperature distribution profiles over time, and flowrate. The in-situ ground temperature distribution profile is measured using Distributed Temperature Sensing System for different hours of the experiment. A detailed, three-dimensional, unsteady-state, finite volume-based computational model has been developed, which solves conjugate fluid-flow and heat transfer phenomena. The simulation outcomes are compared to the results of the experiments. With validated numerical model, to determine the circle of influence, temperature profile of the ground is observed at various radial distances from the borehole. A parametric study is performed by varying inlet temperature of the fluid, mass flow rate, and the thermal conductivity of the ground. The numerical model developed also predicts the temperature recovery behavior of the ground. The results indicate that the average output thermal power for 456 h from the geothermal system ranges from 172 kW to 262 kW based on operating condition chosen and the total thermal energy generated changes between 82 MWh and 194 MWh from a single borehole. After the extraction is terminated, around 86% of the initial ground temperature is restored after 456 h.

Optimum design of a double elliptical latent heat energy storage system during the melting process

This paper concerns the optimum design of double elliptical latent heat storage units during the charging process using three-dimensional numerical simulation. Water and RT35 are employed as the heat transfer fluid and phase change material, respectively. The orientations of both inner and outer elliptical tubes, the number of inner tubes, and the comparison between the straight and wavy configurations for the inner tubes are examined to find the maximum melting rate. Moreover, the sensitivity analysis on the operating conditions, including the Reynolds number and inlet water temperature, is performed. The results show that the best performance is found when the inner and outer tubes are oriented vertically and horizontally, respectively. The performance of the unit enhances as the distance between the inner tube and the bottom wall of the outer tube reduces. Besides, the optimum place for positioning the inner tube is where the minimum distance of the ellipses is 2 mm. It is found that the implementation of double wavy inner pipes increases the heat transfer surface area, which accelerates the melting time by 2.17. The delivered energy rate to the PCM using double wavy inner tubes is 218.75 W/kg, while it is 180.4 W/kg using double straight inner tubes. Eventually, the sensitivity analysis confirms the system is more sensitive to the variations of inlet temperature compared to the Reynolds number regarding the tested operating conditions.

Multi-criteria analysis of a novel biomass-driven multi-generation system including combined cycle power plant integrated with a modified Kalina-LNG subsystem employing thermoelectric generator and PEM electrolyzer

This study proposes a novel biomass-driven multi-generation system composed of five different systems. A gas turbine cycle and a steam Rankine cycle (SRC) are integrated into a system comprised of a modified Kalina cycle in which an expander is used between the two separators, and an LNG regasification system. To recover the waste heat of the Kalina cycle, a thermoelectric generator (TEG) is utilized instead of a condenser for generating electrical power. Total power produced by the expander and TEG is utilized in a proton exchange membrane electrolyzer to produce hydrogen. Domestic hot water and chilled water are, respectively, produced within the condenser of the SRC and the evaporator of the modified Kalina cycle. The results of the base case reveal that the multi-generation system with exergy efficiency of 59.47% is capable of generating power, heating, and cooling rates equal to 44.4 MW, 28.9 MW, and 1.94 MW, respectively. The natural gas mass flow rate is 4.42 kg/s, and the hydrogen flow rate is 5.77 kg/h. Besides, the results demonstrate that the modified Kalina-LNG system in the present configuration is of higher performance than a similar previous research. Finally, it is found that a 100 °C variation in the gas turbine inlet temperature has the greatest effect on the multi-generation exergy efficiency.

Operation characteristics of waste heat recovery from high-temperature particles under varying temperatures and flow rates

High-temperature particles produced from metallurgy, building materials, and chemical industry are mostly characterized by wide variations in temperature and flow rate, and the waste heat recovery processes from these particles are essentially unsteady. The heat transfer characteristics in a gas–solid countercurrent moving bed under periodic variation of inlet particle flow rate and temperature are investigated. The wide variation of inlet particle flow rate and temperature causes wide variation in input heat capacity ratio. However, their effects are different. The inlet particle temperature variation has slight effects on the instant outlet particle temperature and heat recovery efficiency, but great on that of air for the simulated cases. The variation amplitude of outlet air temperature is up to 431.41 K under the wide temperature variation of 600 K and long duration of 2.5τp (τp is the particle residence time). Improving technique should be adopted to maintain the temperature level of outlet air under wide temperature variation according to the utilization of the recovered heat. Meanwhile, the wide variation of flow rate affects the instant outlet particle and air temperatures. The variation amplitudes of outlet particle and air temperature are 88.90 K and 203.35 K, respectively. Furthermore, instant heat recovery efficiency decreases 9.6% under the wide flow rate variation that ranges from 46.58 to 19.96 t/h and long duration of 2.5τp. Varying the flow rate of air flow with an accordance variation range and duration of particle may be an efficient way if the instant heat recovery efficiency and temperature level of outlet air are requested.

Simulation on the Effect of Coolant Inlet Temperature and Mass-Flowrate Variations to the Temperature Distribution in Single Pellet Thermal Reactor Core

An important factor in the development of nuclear energy is reactor safety. The performance of heat transfer from nuclear fuel to coolant is the main key to the reactor safety. This paper presents simulation on temperature distribution in two-dimensional laminar flow for single pellet thermal reactor with variation on temperature inlet and mass-flowrate. The OpenFoam platform (SimFlow 3.1) has been used for the computational and numerical analysis. The simulation is carried out on a single pellet with an aspect ratio of 1.2. The variations in the mass velocity of the coolant flow are 10, 100, and 14300 kg×s-1 with a constant coolant temperature of 552 K, and the variations of the input coolant temperature are 300, 552, and 1000 K with a constant mass-flowrate of 10 kg×s-1. The results obtained from the simulation show that for variations in the input coolant temperature of 300, 552, and 1000 K, the fuel temperature can be reduced respectively by 34, 26, and 14 K. At the fastest variation in the coolant mass-flowrate of 14300 kg×s-1, the coolant temperature around the pellet rises by 396 K. The decrease in fuel temperature is significant if the mass-flowrate of the input coolant flow is relatively low.

Optimum design analysis of a solar-assisted Libr/H2O absorption system with a flat-plate collector

An analytical analysis has been presented to evaluate the performance of a solar-assisted va-pour absorption cooling system with a flat-plate absorber plate. The lithium–bromide water absorption cycle is used to obsstain the cooling effect. The performance parameters, namely absorber plate efficiency, collector efficiency factor, heat removal factor, etc. have been deter-mined with the variation of collector fluid inlet temperature. The cycle coefficient of perfor-mance (COP), system COP, refrigerating efficiency of the cycle, and refrigerating efficiency of the system are determined analytically. The maximum COP and cooling efficiency for both the cycle and system has been found at an optimal collector fluid inlet temperature. The optimum design condition for the variation of different design parameters, such as ambient temperature and thermal conductivity, has also been studied. Finally, the plate material is found to be a minimum at a particular collector fluid inlet temperature which is an optimum design condi-tion to run the solar-assisted vapour absorption system.

Friction reduction by inlet temperature variation in microchannel flow

The problem of viscous resistance significantly hinders the development of effective microsystems for industrial applications, such as chemical analysis and cooling of microelectronics. We present results of experiments and three-dimensional numerical simulations of fluid flow in a rectangular smooth-walled microchannel with a hydraulic diameter of 149 μm. A pressure drop is measured, which depends on the flow rate and temperature of the inlet liquid. To examine the effect of fluid properties, three different liquids are tested, namely, water, ethanol, and methoxynonafluorobutane. The Reynolds number depends on temperature and is varied within the range 68–3011. It is found that the temperature dependence of the liquid viscosity can be used to significantly reduce the pressure drop along the channel. Heating the inlet fluid enables the pressure drop to be reduced by up to 40%. Based on the experimental measurements of the pressure drop in the fluid flow, the wall shear stress is found numerically, thereby allowing correlations to be obtained for the friction factor. The results show that the wall shear stress for numerical simulations can be estimated using the friction factor from the well-known formula with a slight deviation at a high Reynolds number. The experimental results are also in good agreement with the theoretical data for conventional channels.

ANALISIS PENGARUH INLET TEMPERATUR SISTEM PENDINGIN BUATAN TERHADAP KENYAMANAN TERMAL KELAS UNIVERSITAS NUSA PUTRA DENGAN METODE CFD

Air circulation needed to meet comfort standards in classrooms with artificial cooling systems (Air Conditioning) to achieve thermal comfort (Thermal comport), Thermal comfort is one aspect that must be considered when designing a classroom. because at the time of learning there is an accumulation of heat and humidity of the air that will make the room uncomfortable. This research focuses on using the Simulation Computational Fluid Dynamic (CFD) method in the classrooms of Nusa Putra Sukabumi University.
 Simulation using Flovent 10.1 software, the simulated room is a B3D classroom on the 3rd floor of building B of Nusa Putra University which measures 10.15 m x 4.8 m x 3.25 m. The main purpose of this study is to find out the influence of inlet temperature on artificial cooling systems. Through simulation can predict efficiently and effectively setting the temperature inlet of the most optimal artificial cooling system. In the simulation conducted 5 variations, the result is the most ineffective temperature in variation 1, variation 2 and variation 3 at room temperature 16.32 °C – 20.06 °C, belongs to the category of too cold which means the room is uncomfortable. While the room with inlet temperature variation 4 and variation 5 temperature between 21.34 °C – 22.59 °C belongs to the category of comfortable cool based on the thermal comfort standard SNI 03-6572-2001.

Numerical Performance Investigation of Parabolic Dish Solar-Assisted Cogeneration Plant Using Different Heat Transfer Fluids

Parabolic dish solar collectors gain higher solar to thermal conversion efficiency due to their maximum concentration ratio. The present research focuses by integrating the parabolic dish solar collector to the steam cycle producing power and rate of process heating. Pressurized water, therminol VP1, and supercritical carbon dioxide are the examined working fluids in the parabolic dish solar collector. The aim of the current research is to observe the optimal operating conditions for each heat transfer fluid by varying inlet temperature and flow rate of the working fluid in the parabolic dish solar collector, and combination of these parameters is predicted to lead to the maximum energy and exergy efficiencies of the collector. The operating parameters are varied to investigate the overall system efficiencies, work output, and process heating rate. Findings of the study declare that water is an efficient heat transfer fluid at low temperature levels, whereas therminol VP1 is effective for a higher temperature range. The integrated system efficiencies are higher at maximum flow rates and low inlet temperatures. The efficiency map of solar collector is located at the end of study, and it shows that maximum exergy efficiency gains at inlet temperature of 750 K and it is observed to be 37.75%.

Investigation of the performance of a transcritical CO2 heat pump system subject to heated water conditions: Perspective from the second law

• A rational model of CO2 heat pump cycle is studied based on second-law perspective. • The effect heat source on the transcritical CO2 heat pump is analyzed in details. • The effects of irreversibility for every component on optimal discharge pressure are discussed. • Optimal discharge pressure is independent of compressor, and evaporator. • Optimal discharge pressure is mainly control by the thermal characteristics of gas coolers. For the past two decades, appreciable efforts are made to predict the optimal discharge pressure ( P opt ) of carbon dioxide (CO 2 ) transcritical system. These approaches are normally empirically derived and were limited to relevant conditions. The deviations may be also related to the inlet or outlet temperatures of the secondary fluid in the heat pump gas cooler. Thus, this study aims to develop a rational method to predict optimum discharge pressure based on the simulated data through exergy analysis. To simplify the simulation, the model assumes the constant heat transfer capacity ( UA) within the evaporator, and the model is verified with a 70 kW trans-critical CO 2 heat pump system. The influence of inlet (10–45 °C) and outlet (40–90 °C) water temperature on the system performance are examined from the perspective of the first and the second law of thermodynamics. The detailed exergy analysis for the cycle and each component is elaborated in detail subject to discharge pressure. It is found that the maximum COP declines but the P opt rises upon variable outlet temperature and inlet temperature of heated water. The P opt is mainly controlled by a gas cooler when compared to other components. The irreversibility of the gas cooler accounts for 3% to 3.6% of total heating capacity when P opt occurs regardless of the inlet or outlet water temperature. The corresponding maximum COP is about 4 times larger than the reciprocal of the irreversibility rate of the compressor. Yet, a new strategy is proposed to predict the P opt in terms of the irreversibility of the gas cooler. The proposed method is rationally based and can quickly diagnose the P opt through the four terminal thermal states instead of continuous monitoring the local maximum COP . Compared with the eight existing correlations listed in Appendix, the proposed novel method yields the least average and standard deviation of 2.6% and 3.1%, respectively when compared to the existing correlations.

Numerical Analysis of Heat Transfer on the Shell Side of a Helically Coiled Tube Heat Exchanger for Helium Applications

Abstract A new heat transfer correlation for high temperature helium on the shell side of a helically coiled tube heat exchanger was derived with the use of computational fluid dynamics (CFD) tools. The use of suitable heat transfer correlations has an impact on the evaluation of performance of a heat exchanger in relation to the requirements for a sufficient heat transfer surface, which relates to material cost requirements; therefore, it is of high importance. A numerical model was validated with data measured using the helium cooler, which is part of an experimental channel located at the Research Center Řež (CVR) in the Czech Republic. The numerical model used for obtaining the heat transfer correlation assumes a constant heat flux on the wall of the helical coil. In total, 72 cases with varying inlet temperatures, velocities, and heat fluxes were simulated to obtain the heat transfer correlation. Furthermore, the effects of the flow rectifier within the channel regarding the heat transfer coefficient and pressure loss were discussed.

Experimental performance analysis of a CO2 direct-expansion solar assisted heat pump water heater

Abstract In the past decades, combined solar energy with heat pump systems has been one of the very widespread ways to improve the efficiency of conventional heat pumps. In that way, this paper presents an experimental analysis of the influence of environmental conditions in a small size DX-SAHP operating with CO2 as refrigeration fluid to heat water. The variation of the water inlet temperature, the solar radiation flux and the relative humidity are analyzed and 88 different experimental results are presented. To support the analysis, a thermographic camera was also used. The results show that the gas cooler outlet pressure and temperature are strongly influenced by the water inlet temperature. As the water inlet temperature increases, the gas cooler outlet pressure and temperature increase, and consequently the COP decreases. The COP decreases in 45.8% for the variation of the water inlet temperature to 15–35 oC. The variation of the solar radiation of 876.9–30.17 W.m-2 presents a reduction of performance in about 30%. For the same conditions for the water heat exchange, the pressure ratio of the cycle decreases with an augment on the solar radiation flux. In addition, the COP is higher in 6% for a change in the mean relative humidity of 31.6–55.8 %.

Performance comparison of annular and flat-plate thermoelectric generators for cylindrical hot source

Utilizing the heat energy of exhaust gases is a promising application of thermoelectric generator (TEG), which can convert low grade thermal energy into electricity. The annular thermoelectric generator (ATEG) is thought to be much more feasible for cylindrical heat source compared to the flat-plate thermoelectric generator (FTEG) in reference to the compatibility. Nevertheless, the quantitative comparison is lacking to clarify the prevalent geometry of TEG for cylindrical heat source. In this work, the performances of ATEG and FTEG are compared in detail with varying inlet temperature, velocity and the convective heat transfer coefficient when cylindrical heat source is applied. The turbulent heat source is described by the standard κ-ɛ functions together with the two-equation heat transfer model, while the output power and conversion efficiency of the ATEG and FTEG are calculated by solving the coupled thermo-electric equations. Our results showed that the output powers and the conversion efficiencies of ATEG and FTEG both increase with the increase of the inlet velocity, temperature, and the convective heat transfer coefficient. The conversion efficiency of ATEG is always higher than that of FTEG. The conversion efficiency of ATEG becomes even larger than that of FTEG when inlet temperature and/or convective heat transfer coefficient are relatively larger. In contrast, the output power of ATEG has no obvious difference with that of FTEG. This study addressed the condition when the ATEG has obvious advantage compared to the FTEG with cylindrical heat source applied. Our results suggest the annular TEG is better choice for cylindrical hot source especially when the inlet temperature and/or convective heat transfer coefficient are relatively larger. It could be a helpful guide for choosing suitable geometry of TEGs for energy harvesting in complex condition.

KAJI KARAKTERISTIK PERPINDAHAN PANAS PENGARUH BELOKAN TAJAM PADA PENUKAR KALOR TIPE TUBE

Using the thermal machines in the production process or overdone heat power operation require unit of Heat Exchanger (HE) having high level heat transfer coefficient (hc) for transferring to the thermal reservoir. Experimental studies have been done for heat transfer characteristics of forced convection on the round duct with method use that compare three of heat exchanger with a variety of pipe bends and a long pass after a turn that is different. HE pipes have length of tube 500 mm with a 12 bends, HE pipes length of tube 250 mm with 24 bends and HE pipes length of tube 125 mm with 48 bends. The heat fluid flowed into the tube, and the tube is immersed in the cold water tank. For each of test equipments can be done three times experiment with different variations in inlet temperature that is at 600C, 700C and 800C, with a duration of 5 minute intervals for 50 minutes. Many pipe bends and short passes after a HE will increase turbulence flow pattern. The high of turbulence will increase the value of heat transfer coefficient, but it can hold on fluid flow rate. Keywords : heat transfer characteristics, round duct, sharp bends, long pass

Modeling Reactor Noise due to Rod and Thermal Vibrations with Thermal Feedback Using Stochastic Differential Equations

Fluctuations associated with power and detector readings in a nuclear reactor, commonly known as reactor noise, are of great importance in nuclear science and engineering. Two different types of noise are described in the literature: internal noise, which is associated with the inherent stochasticity of fission chains, and external noise, which is governed by physical fluctuations of the macroscopic system. The latter may include temperature fluctuations, vibration of regulation rods, fluent turbulence, bubble formation, and more. It is generally true that in power reactors, where high temperatures and strong hydrodynamic flows are characteristic, the external noise is dominant. The goal of this paper is to propose a stochastic differential equation (SDE) that models the effect of two types of external noise terms: the inlet temperature variations, which affect the power through reactivity feedback, and rod vibrations, which affect the reactivity directly. Although these aspects were studied in the past, they were only treated via nonstochastic equations. It is argued that the SDE approach, previously used only for modeling the effect of internal noise on nuclear reactor dynamics, is also highly suitable for modeling external noise. The main advantage of our approach is the ability to arrive at analytic formulas. The contributions presented in this paper based on the SDE approach are as follows. Under a linear approximation of thermal feedback, the stabilizing effect of thermal feedback is explained and quantified, and a limiting distribution is analyzed in full. An analysis of the detector response on a finite time interval is carried out, leading to a version of the Feynman variance-to-mean-ratio formula in the presence of external noise. Finally, a calculation of the eigenvalues associated with the linearized system alluded to above is performed, showing that in practical cases the rod vibrations and inlet temperature fluctuations correspond to eigenvalues in distinct timescales. The significance of these finding is discussed.

Transient analysis and control of a heat to power conversion unit based on a simple regenerative supercritical CO2 Joule-Brayton cycle

Supercritical carbon dioxide (sCO2) heat to power systems are a promising technology thanks to their potential for high efficiency and operational flexibility. However, their dynamic behaviour during part-load and transient operation is still not well understood and further research is needed. Additionally, there is not enough literature addressing suitable control approaches when the objective is to follow the dynamics of heat load supplied by the topping process to maximise the power recovery. The current research aims to fill these gaps by proposing a one-dimensional transient modelling formulation calibrated against the major components of a 50 kWe sCO2 test facility available at Brunel University London. The dynamic analysis showed that the system quickly adapts to a 2800s transient heat load profile, proving the flexible nature of the sCO2 system investigated. The turbine by-pass, during startup and shutdown modes of operation, enabled gradual and safe build-up/decline of the pressures and temperatures throughout the loop. The regulation of the inventory in the range 20–60 kg allowed a 30% variation of the turbine inlet temperature with lower penalties on system performance than the turbomachinery speed control. The designed proportional-integral inventory controller showed a rapid response in the control of the turbine inlet temperature around the set point of 773 K during large variations of the heat load.

Multi-stage heat-pipe heat exchanger for improving energy efficiency of the HVAC system in a hospital operating room 1

Abstract The demands of specific requirements related to thermal comforts, such as temperature, relative humidity, inside air exchange and other factors required in a hospital operating rooms, have necessitated the development of energy-efficient heating, ventilation and air conditioning (HVAC) systems and efficient heat-recovery system using a heat-pipe heat exchanger (HPHE). The experiment was conducted by using HPHEs having three, six and nine rows, with four heat pipes in each row, arranged in a staggered configuration with a variation of fresh-air inlet temperature and velocity. The theoretical analysis was conducted using the ε-NTU method for predicting the effectiveness, outlet temperature of the evaporator side and energy recovery of the HPHE. The experimental results indicated that increasing the air-inlet temperature in the evaporator section and the number of rows increased the HPHE effectiveness but increasing the air-inlet velocity reduced the effectiveness. The highest effectiveness of 62.6% was obtained at an air-inlet temperature of 45°C with an air-inlet velocity of 2 m/s and a 9-row HPHE. The energy recovery of the HPHE increased with the number of rows, air-inlet temperature and air velocity in the evaporator section. The ε-NTU method can be used as a comparison method in the analysis of heat-recovery systems that apply HPHE air conditioning systems. Heat pipes that utilize cold-air exhaust from a room in an HVAC system can enhance efficiency and reduce emissions.

Thermodynamic, Exergy and Environmental Impact Assessment of S-CO2 Brayton Cycle Coupled with ORC as Bottoming Cycle

In this article, a thermodynamic, exergy, and environmental impact assessment was carried out on a Brayton S-CO2 cycle coupled with an organic Rankine cycle (ORC) as a bottoming cycle to evaluate performance parameters and potential environmental impacts of the combined system. The performance variables studied were the net power, thermal and exergetic efficiency, and the brake-specific fuel consumption (BSFC) as a function of the variation in turbine inlet temperature (TIT) and high pressure (PHIGH), which are relevant operation parameters from the Brayton S-CO2 cycle. The results showed that the main turbine (T1) and secondary turbine (T2) of the Brayton S-CO2 cycle presented higher exergetic efficiencies (97%), and a better thermal and exergetic behavior compared to the other components of the System. Concerning exergy destruction, it was found that the heat exchangers of the system presented the highest exergy destruction as a consequence of the large mean temperature difference between the carbon dioxide, thermal oil, and organic fluid, and thus this equipment presents the greatest heat transfer irreversibilities of the system. Also, through the Life Cycle Analysis, the potential environmental impact of the system was evaluated to propose a thermal design according to the sustainable development goals. Therefore, it was obtained that T1 was the component with a more significant environmental impact, with a maximum value of 4416 Pts when copper is selected as the equipment material.

Numerical analysis on thermal–hydraulic performances of staggered tube bundles for an aero-engine compact precooler

The deeply precooled air-breathing technique is an effective approach to cool down the extreme hot incoming air for hypersonic engine. This paper investigates the thermal performance of staggered mini-tube bundle as the compact precooler for aero-engine application. The coupling heat exchange between the hot air and in-tube coolant is explored. Two methods (i.e., surface temperature method and LMTD method) are used to evaluate the airside heat transfer characteristics. Comparison of predicted Nusselt number and empirical correlations shows that both methods have acceptable discrepancies, especially for surface temperature method. In addition, Nusselt number predicted by the surface temperature method almost keeps identical at different coolant velocities, while the LMTD method is sensitive to the flow velocity of in-tube coolant. In order to better understand the influences of boundary conditions, the detailed analysis for parameters such as inlet pressure, inlet temperature, transverse pitch, coolant velocity and property variation on thermal performance of the tube bundle is carried out.