4-1 ConclusionsFrom the experimental results presented and discussed in the previous chapter, the following conclusions may be made :1- The heat transfer characteristics of tubes in fixed volume , bothfor staggered and in-line arrangements are better than those forsingle tube at the same conditions .2- Staggered arrangements of tubes in fixed volume gives better heat transfer coefficient compared with in line one and at the same conditions .3- The optimal tube spacing for different arrangements at is Sh /d and S/d = 1 at S/d = 1 , for both in-line and staggered arrangements.4- A correlation for in-line and staggered arrangements of the present data are developed. This correlation satisfactorily expresses the influences of Re, Pr, and cylinder spacing on the Nusselt Number Nu . The correlation can be used to predict the heat transfer coefficient with reasonable accuracy not exceeding ± 30% of measured values.4-2 Recommendations For Future WorkFrom the experimental study of heat transfer coefficient of single smooth tube, in-line and staggered arrangements of smooth tubes in a fixed volume , we recommend the following research points for the future work as follows:1- Heat transfer coefficient of the different arrangements with anther Sh/d and S/d for both in-line and staggered arrangements in the different fixed volumes.2- Heat transfer coefficient of enhanced tubes surface at the same conditions for both in-line and staggered arrangements in the same fixed volume.3- Optimum design of tube surface enhancement for both in-line and staggered arrangements .4- Study the effect of using hot and moist air on the heat transfer coefficient of the same different arrangements ( in-line and staggered) in the same fixed values.4-1 ConclusionsFrom the experimental results presented and discussed in the previous chapter, the following conclusions may be made :1- The heat transfer characteristics of tubes in fixed volume , bothfor staggered and in-line arrangements are better than those forsingle tube at the same conditions .2- Staggered arrangements of tubes in fixed volume gives better heat transfer coefficient compared with in line one and at the same conditions .in design and construction aspects, the field of concrete repair is rapidly increasing dueto premature failures. Which is due to the rapid constructional development in desertand coastal regions where severe atmospheric and environmental conditions prevail.The majority of failures are associated to chloride induced reinforcement, wherestructures undergo the most severe type of corrosion exposure that increases with thesuccessive wetting and drying of the tide.The main objective of this research is to simulate the tidal exposure of marineenvironments and study the chloride induced corrosion process of structuralreinforcement. The research also includes the efficiency evaluation of some protectionmethods and repair materials used to arrest and delay the chloride induced corrosion ofsteel reinforcement.The research program consisted of the three phases, the first phase spanned for aperiod of 15 months and it consisted of 48 reinforced beams and 48 concrete cubes. Itaimed to study the effect of chloride salts on the reinforcement corrosion process byevaluating the degree of chloride contamination and assess the degree of corrosiondamage. The second phase spanned for a period of 20 months and it consisted of 36reinforced beams. It aimed to evaluate the efficiency of three protection methods(concrete surface coating, steel surface coating and concrete surface impregnation) thatwere used to combat chloride induced corrosion of steel. The third phase spanned for aperiod of 20 months and it consisted of 36 reinforced beams. It aimed to evaluate theefficiency of three repair materials (cement based, rubber based and epoxy based) usedas a reinforcement barrier to combat chloride induced corrosion of reinforcement.The tidal exposure of marine and coastal environment was simulated inlab bysubjecting specimens to cyclic successive wetting and drying (SWD) in saline solutionswith varying chloride concentrations (0, 1.5,3.5 and 5.0 % NaCl) for different exposuredurations (150, 300, 450 and 600 SWD cycles). Cube specimens were tested forcompressive strength and pulverized mortar samples were extracted at the cover depths0.5, 2 and 5 cm for chloride ion profiles determination. Reinforced beam specimenswere tested for their flexural strength capacity by the four point bending test todetermine the load capacity reduction caused by chloride induced corrosion andaccordingly assess the degree of damage.