تصميم وبناء مجمع جديد للمياه بالطاقة الشمسية باستخدام حقن الفقاعات الهوائية

Design and Construction a Novel Solar Water Collector with Air Bubble Injection

Abstract

This study presented two investigation ways (numerically and experimentally) that used a venturi mechanism to inject air bubbles into a wavy pipe solar water collector to improve its performance. This technique allows air to move through the pipes, mixing with water and then flowing together inside the solar collector’s pipe. Two systems were used in each part, an opened and closed system. The numerical part was accomplished by generating the geometric model with SOLID WORKS 2021, followed by being simulated with using the simulation program ANSYS 21. While the experimental part was executed by constructing a rig of the solar water collector system with collector dimensions of (120 x 80 x 24) cm3 that is inclined by 45o, which includes a wavy copper pipe shape with a diameter of 0.0125 m and a length of 8 m that is painted with matt black color. The test rig was construct in Karbala city to figure out the effect of air bubble injection under the weather conditions of the city of Holy Karbala in Iraq with latitude and longitude of 32.616° N and 44.0249° E during the first months of the year (January, February, March and April). The water as a working fluid was used with multiple flowrates to determine the collector efficiency of each system, then the air bubbles were injected with several discharges to the most efficient water flowrate for each system (closed and opened), thus knowing the best flowrate of the air-water mixture for each system.
In this work, fourteen cases were simulated and experimented to find out the collector performance and the most efficient case, which consisted of four various levels of only water flowrates of (0.5, 1, 1.5 and 2) L/min as a working fluid for an opened and closed system. The air bubbles were injected at three air flowrates of (0.15, 0.25 and 0.35) L/min mixed with the most efficient water flowrate at each system.
However, the system efficiency was calculated after the numerical and experimental tests were done for the four water flowrates for both systems. The calculation shows that the most efficient case for the opened system occurred when the water flowrate was 1 L/min, with an average efficiency of (31.8) %, whereas the most efficient case for the closed system was at 2 L/min, with an average efficiency of (45.5) %. The three different flowrates of air were injected into the efficient casing for each system. The result showed that the closed system efficiency was enhanced by (24.98%), (37.28%), and (53.71%), whereas the opened system efficiency enhanced by (30.89%), (37.92%), and (20.03%) after adding air at flowrates of (0.15, 0.25, and 0.35) L/min respectively.
Numerical simulation, by ANSYS FLUENT software and experimental results, for the model were found, to have a fairly, good agreement, under the same, conditions. For the both systems (with and without air bubbles injection), the maximum percentage of difference in the results is no more than 13.5%.