Summary Stationary solar collector such as flat‐plate collector is a thermal device, which traps solar energy and converts it into heat that can be used in industrial and domestic applications such as water heating. Flat‐plate collector thermal performance enhancement is investigated in this research paper. Two cross‐sectional geometries of the tube in the heat exchanger were investigated; a normal circular tube and a twisted tube were used in the experiment. The aim of the twisted tube exchanger is to enhance the performance of heat transfer of the tubes and to reduce the shell pressure drop; flat‐plate solar collector is the used application to study the heat exchanger performance. Both twisted tubes heat exchanger and normal circular tubes heat exchanger were examined in the same location and conditions with the same solar collector, both were used in the heat exchanger to study their effect, with two different working fluids, which are distilled water and multiwalled carbon nanotube (MWCNT)/water nanofluid. The system shows an increase in the performance when twisted tubes were used in the system compared with the circular tubes in both distilled water and MWCNT/water nanofluid by 12.8% and 12.5%, respectively, with an improvement by 34% for twisted tubes with MWCNT compared with normal circular tubes with distilled water.

Background: Malnutrition is a major health related concern associated with higher morbidity and mortality in the elderly compared to their younger counterparts. Malnutrition is not an inevitable side effect of ageing, but many changes related to ageing can cause malnutrition. The early recognition of patients at high risk of malnutrition is needed to timely manage the condition and avoid its adverse outcomes. Several types of nutrition screening tools have been developed for evaluating the nutritional status of elders; however, the Mini-Nutritional Assessment-Short Form (MNA-SF) is the most widely used tool. Aim: The aim of this study is to identify the most appropriate nutritional screening tool for use in hospitalized elderly population. Method: Mini-Nutritional Assessment-Short Form (MNA-SF), Malnutrition Universal Screening Tool (MUST), The Nutritional risk screening (NRS), Patient-Generated Subjective Global Assessment (PG-SGA) and Geriatric nutritional risk index (GNRI) were administered to 20 patients. All patients were 60 years and over. Results: Using the MNA-SF 12 (60%) of the studied sample were malnourished and 8 (40%) had normal nutritional status. Tools performance in predicting malnutrition was calculated. The sensitivity was 91%, 83%, 83% and 66% and specificity was 50%, 62%, 12% and 75% with the NRS, MUST, PG-SGA and GNRI, respectively. Combining different pairs of tools MUST and NRS together had better sensitivity 92.8% and specificity 66.6% then 2nd better two tools together is NRS and GNRI with sensitivity 91.6% and specificity 50% with accuracy 75% other tools showed high sensitivity but low specificity as PGSGA with NRS and PGSGA and GNRI. Conclusion: NRS had the highest sensitivity while GNRI had the highest specificity among different studied assessment tools. MUST and NRS together had better sensitivity but lower specificity than either tool alone. Combining the NRS and GNRI had better sensitivity than GNRI alone and better specificity than NRS alone. We recommend using NRS alone as the optimal screening tool.