One of the most recently important heat exchangers is the Printed circuit heat exchanger especially in the nuclear power plant and aerospace applications due to its very compact geometry and small print foot. This paper presents a 3D numerical investigation on the thermo-hydraulic performance of PCHE with new non-uniform channel design configuration. The new channel design is a rectangular cross section with repeated converging diverging sections or periodic diamond shape. The influence of three design parameters on the heat exchanger performance was studied and optimized, pitch length (p), length ratio (β) and the converging diverging angle (α). The computational models investigated in this study based on the operating conditions of the intermediate heat exchanger of very high temperature gas cooled reactor with helium as the working fluid under operating pressure of 3Mpa and inlet temperature of 800 K. The Reynolds number varied from 200 to 2000. Different Pitch lengths were used (1.59, 3.18, 6.36, and 12.73) mm, and different C-D angle (0, 4.5, 6, 7.5, 9, 10.5 and 12) and also different length ratios were used (0.2, 0.25 and 0.333). Three performance parameters were studied the Nusselt number, friction factor and the overall performance evaluation factor. Results show that the thermal performance enhanced with decreasing the pitch length and with increasing C-D angle and it was shown that this enhancement was found only at high Reynolds number above 1400. The best performance obtained at p=3.18, α=6 and β=0.25 based on the overall evaluation performance.

The phase change materials (PCM) is commonly used for storage heat as a latent heat, the main disadvantage of this method is slow response time during charging and discharging; this due to the PCM thermal properties. This work studied experimentally the enhancement of thermal properties of PCM by adding various metallic swarf such as copper, aluminum and iron swarf. Metallic swarf used as thermal conductivity promoter to produce modified paraffin wax samples. The addition of the previous enhancers was conducted with a weight fraction of (7.5%, 12.5% and 17.5%) to the whole weight of the mixture. The experimental results showed that adding of metallic swarf to the PCM decrease the charging time by (5.5-22.1%) for weight fractions from (7.5-17.5%) respectively. The addition of metallic swarf to PCM showed enhancement of discharging time by (27-77 %) compared with the case of pure wax for copper swarf weight fraction of (7.5-17.5%) respectively. Thermal conductivity of PW was enhanced by using aluminum, copper, and iron swarf, where it is found that the maximum enhancement about (53 times) due to the addition of (17.5%) of aluminum swarf. This method is considered a successful economic way due to the use of manufacturing waste.

Film cooling is one of the methods used to protect the surfaces exposed to hightemperature flows, such as those exist in gas turbines. It involves the injection of coolant fluid (at a lower temperature than that of the main flow) to cover the surface to be protected. This injection is through holes that can have various shapes; simple shapes, such as those with straight cylindrical or shaped holes (included many holes geometry, like conical holes). The computational results show that immediately downstream of the hole exit, a horseshoe vortex structure consisting of a pair of counter-rotating vortices is generated. This vortex generation affected the distribution of film coolant over the surface being protected. The fluid dynamics of these vortices are dependent upon the shape of the film cooling hole, and blowing ratio, therefore the film coolant coverage which determines the film cooling effectiveness distribution and also has an effect on the heat transfer coefficient distribution. Differences in horseshoe vortex structures and in resultant effectiveness distributions are shown for cylindrical and conical hole cases for blowing ratios of 0.5 and 1. The computational film cooling effectiveness values obtained are compared with the existing experimental results. The conical hole provides greater centerline film cooling effectiveness immediately at the hole exit, and better lateral film coolant coverage away of the hole exit. The conical jet hole enhanced the average streamwise adiabatic film cooling effectiveness by 11.11% and 123.2% at BR= 0.5 and 1.0, respectively, while in the averaged lateral adiabatic in the spanwise direction, the film cooling effectiveness enhanced by 61.75% and 192.6% at BR= 0.5 and 1.0, respectively .

The present work investigated experimental and numerical the effect of internal radiate on the external tube on heat transfer coefficient and pressure drop in tube for range of Reynolds Number of (4000-16000). The study also discuss the different in results between the slot dimple tube and plain tube. Heat transfer and pressure drop for test tube were evaluated and presented as dimensionless value by Nusselt number and friction factor. Overall enhancement ratio of dimpled tube is discussed. Thermal and hydrodynamic results of CFD study are presented in form velocity vector and contour of local heat transfer coefficient. The results comparison of Nusselt number between plain tube and present slot dimples tube, shows that slot dimples tube enhance the heat transfer between 1.584 - 2 times the plain tube, and When compare between experimental and correlated Nusselt number for present slot dimple tube, the result show deviation in the test range of Reynolds number. The numerical results were in good agreement with the present experimental results. The deviation is within 6 - 22% higher for numerical at low and high Reynolds number, respectively. The overall enhancement ratio for present slot dimpled tube dependent on plain tube, the result depict that the slot dimple tube gave high enhancement in heat transfer relative to plain tube. The enhancement ratio is varied from (1.09 to 1.15) for range of Reynolds numbers between (4000 to16000).

Enhancing heat transfer efficiency is crucial for the performance of heat exchangers, and the implementation of corrugated tubes has been shown to be an effective approach. In this study, a numerical investigation was conducted to analyze the impact of varying corrugation depths in rod baffles and two types of corrugated tubes (1 start and 3 start) on heat transfer and pressure drop characteristics. Water was used as the working fluid on the shell side of the heat exchanger, while a constant wall temperature was maintained on the tube side. Corrugation ratios (e/dh) of 0.1 and 0.13, pitch (p) of 10, 20, and 30 mm, and two types of rod baffle spacing (x/d) of 1.25 and 1.375 were considered. The analysis was performed in the turbulent flow regime with Reynolds numbers ranging from 4,000 to 24,000. Three-dimensional governing equations were solved using the standard k-ε model in ANSYS-Fluent 18.1 to examine the flow behavior within the corrugated tubes. The results indicated that a primary vortex was formed in the main flow due to the induced rotational flow along the helical path, as well as a secondary vortex behind the rib. These vortices disrupted the boundary layer and promoted flow mixing between layers. The average Nusselt number for corrugated tubes (pitch 10 mm) increased by 25% and 55% for corrugation depths of 0.1 and 0.13, respectively. However, the friction factor for corrugated tubes with (e/dh) = 0.1 and 0.13 was found to be higher than that of smooth tubes by 66%, 133%, and 130%. With the incorporation of both corrugated tubes and rod baffles, the thermal enhancement factor reached 1.9 for x/d = 1.25 and 1.97 for x/d = 1.375 at the same pumping power (50 mm). This study provides valuable insights into the effects of corrugated tubes and rod baffles on heat exchanger performance for various Reynolds numbers.