Applications of Metaheuristic Algorithms in Solar Air Heater Optimization: A Review of Recent Trends and Future Prospects

Table 4

Comparison of thermal or thermohydraulic performance of SAHs using various metaheuristic algorithms for SAH optimization.

S. no.	Author(s), year(s), and references	Types of SAHs	Metaheuristic algorithm(s)	Important considered input/design/operating parameters for optimal performance (efficiency)	Thermohydraulic/thermal performance (efficiency)	Comments
1.	Siddhartha et al. (2012) [14]	A smooth flat plate SAH (SFPSAH)	PSO	(i) Number of glass covers (): 3; (ii) Solar irradiance (): 600.0 W/m^2; (iii) Wind velocity (): 1.0 m/s; (iv) Tilt angle : 68.36°; (v) Plate emissivity (dimensionless) : 0.89; (vi) Ambient temperature of air : 280.43 K	The maximum thermal efficiency: 72.42%	(i) The increasing Reynolds number (Re) leads to a better heat transfer rate and enhanced thermal efficiency at  W/m^2.; (ii) The thermal efficiency of SFPSAH was improved using a greater number of and the same value of  W/m^2.; (iii) The maximum thermal efficiency for three glass cover plates was found at .; (iv) By increasing the solar radiation intensity, the thermal performance decreased.
2.	Mohanty et al. (2020) [194]	A three-sided roughened SAH	MOPSO	(i) Re: 12,000.0–13,000.0; (ii) Applicable pitch roughness: 10.0; (iii) Applicable roughness height: 0.3–0.4; (iv) Mass flow rate : 0.04 kg/s	The greatest thermal efficiency range: 63.0–75.0%	(i) The Reynolds number and applicable pitch roughness were the most dominant parameters for both responses.; (ii) The applicable roughness height had little variation effects on both responses.; (iii) Both the enhanced Nusselt and Reynolds numbers weakened the applicable pitch roughness.
3.	Kumar and Layek (2019) [84]	A roughened SAH (twisted rib roughness)	PSO and TLBO	(i) Twist ratio : 3; (ii) Pitch-height ratio : 8; (iii) Re: 21,000.0; (iv) Rib inclination angle : 60.0°	Experimentally, 2.13 was the highest thermohydraulic efficiency.; The optimal results for the highest thermohydraulic efficiency obtained by PSO and TLBO techniques were 2.105 and 2.117, respectively.	(i) The optimum thermohydraulic efficiency was obtained at a lower value and decreases with an increasing ratio.; (ii) The TLBO showed a better optimal solution than the PSO algorithm.
4.	Rao and Waghmare (2015) [24]	A smooth flat plate SAH	TLBO	(i) Wind velocity: 1.2729 m/s; (ii) Tilt angle: 59.5832°; (iii) Plate emissivity: 0.8835; (iv) Ambient temperature: 293.9362 K; (v) Temperature rise: 2.1395 K; (vi) Irradiance: 600.0 W/m^2; (vii) Reynolds number: 20,000.0	The maximum thermal efficiency: 76.67%	(i) The thermal efficiency increases with the Reynolds number.; (ii) The thermal efficiency slightly increases with the glass cover plates.; (iii) The solutions obtained from the TLBO algorithm were better than alternative metaheuristic algorithms like GA, PSO, and SA. Therefore, for the same considered problem, the TLBO was better than alternative optimization techniques in the newly published literature.
5.	Rao (2016) [200]	A smooth flat plate SAH	TLBO and ETLBO	(i) Wind velocity: 1.3194 m/s; (ii) Tilt angle: 60.4883°; (iii) Plate emissivity: 0.8947; (iv) Ambient temperature: 292.5993 K; (v) Temperature rise: 2.1448 K; (vi) Irradiance: 600.0 W/m^2; (vii) Reynolds number: 20,000.0	The highest thermal efficiency: 76.7881% (applying ETLBO)	(i) The thermal efficiency increases with the Reynolds number.; (ii) The thermal efficiency slightly increases with glass cover plates.; (iii) The ultimate solutions obtained from the TLBO and ELTBO algorithms were better than alternative metaheuristic algorithms like GA, PSO, and SA. Hence, TLBO and ELTBO algorithms were found to be more effective.
6.	Varun and Siddhartha (2010) [202]	A smooth flat plate SAH	GA	(i) Air velocity: 2.95 m/s; (ii) Tilt angle: 65.33°; (iii) Plate emissivity: 0.86; (iv) Ambient temperature: 296.11 K; (v) Temperature rise: 2.20 K; (vi) Irradiance: 600.0 W/m^2; (vii) Reynolds number: 20,000.0	The highest thermal efficiency: 75.65%	(i) The thermal efficiency of a flat plate SAH increases with the Reynolds number.; (ii) The highest thermal efficiency was obtained applying many system design parameters.
7.	Şahin (2012) [203]	SAC	ABC and GA	(i) Velocity: 3.6859 m/s; (ii) Collector slope: 40°; (iii) Absorber plate emissivity: 0.9415; (iv) Emissivity of glass covers: 0.8043; (v) Air temperature: 290.0798 K; (vi) Irradiance: 600.0 W/m^2; (vii) Reynolds number: 6,000.0	The optimum thermal efficiency: (i) ABC: 0.7998; (ii) GA: 0.7983	(i) ABC and GA optimization solutions were more precise than traditional methods.; (ii) The results show that both the ABC and GA techniques were profitably applied for the thermal SAC efficiency optimization. However, the ABC algorithm was preferable to the GA.; (iii) The thermal efficiency of a SAC increases with the Reynolds number.
8.	Saravanakumar et al. (2020) [159]	Joined fins and stopper coarse arc-shaped rib SAH	GA	(i) Fin number: 8; (ii) Baffle length: 0.2 m; (iii) Baffle width: 0.015 m; (iv) Mass flow rate: 0.012 kg/s	The highest exergy efficiency: 5.2%	(i) Higher optimum thermal efficiency leads to a greater mass flow rate, and more exergy destruction is observed between the plate and the sun.; (ii) Exergy efficiency was assessed based on exergy destruction and losses.; (iii) GA optimized parameters with maximum exergy efficiency of 5.2%.; (iv) Optimum values were obtained for design and operating parameters.; (v) Results of model simulations for proposed SAH were validated with the models available in the recent literature.
9.	Gholami et al. (2019) [204]	A SAH with arcuate-shaped obstacles	NSGA-II	(i) Range of flow rate (kg s^-1): 0.001–0.5; (ii) Inlet temperature range (K): 273.0–300.0; (iii) Inlet temperature range (K): 273.0–410.0; (iv) Range of area (m^2): 1.0–5.0; (v) Solar irradiance (W m^-2): 800.0	Exergy efficiency of collectors with obstacles: 3.5%	(i) Their results indicate that both the double glass cover and obstacle (type III) SAHs were more efficient in terms of economic and exergetic characteristics than the alternatives considered in their study.
10.	Yıldırım and Aydoğdu (2017) [23]	Flat plate SAHs: (i) Single-pass SAH; (ii) Double-parallel pass SAH	ABC	The optimum channel depth and optimum air mass flow rates were both evaluated for different collector lengths and different solar radiations. Their analysis and comparisons were shown in tables in [23].	The maximum thermohydraulic efficiency: (i) Single-pass SAH: 71.43%; (ii) Double-parallel pass SAH: 82.91%	(i) The ABC optimization technique was found to be applicable to optimize the SAHs.; (ii) Some design parameters like the channel depth and air mass flow rate can be assessed for optimum thermohydraulic efficiency.; (iii) Optimum thermohydraulic efficiency decreased with increasing collector lengths.; (iv) Thermal efficiencies corresponding to maximum thermohydraulic efficiencies decreased with increasing collector lengths.; (v) The optimum channel depth increased with increasing collector lengths.; (vi) Solar insolation increased the heat gain and enhanced both the thermal efficiencies and thermohydraulic performance.
11.	Siddhartha et al. (2012) [210]	Flat plate SAH	SA	(i) Wind velocity: 1.0 m/s; (ii) Tilt angle: 70.0°; (iii) Irradiance: 600.0 W/m^2; (iv) Plate emissivity: 0.85; (v) Reynolds number: 20,000.0	The optimized thermal efficiency: 72.48%	(i) The thermal efficiency of a flat plate SAH increases with the Reynolds number.; (ii) The thermal efficiency of a flat plate SAH increases with the number of glass cover plates and tilt angle.; (iii) Upon comparison with the GA, the empirical SA optimal thermal efficiencies were similar to GA. However, the GA values were higher than SA estimates.