Table 9.

Comparison of pulsating flow studies and parabolic trough collector research.

Study	Flow type	Geometry	Method	Gap filled	Key findings	Key limitations	Ref
Present work	Unsteady pulsating flow coupled with MCRT algorithm	SEGS LS-2 PTC	Numerical	Combined effects of frequency and dimensionless amplitude on SEGS LS-2 thermal performance	77% thermal efficiency at Fe= 5 Hz (St=0.131), A=0.5	_	_
Dudley et al.	Steady flow	SEGS LS-2 PTC	Experimental	Baseline thermal efficiency and heat loss reduction	70% efficiency	baseline steady conditions and no efficiency improvement	2
Kurtulmus et al.	Pulsating flow	Sinusoidal channel	Experimental	Studied pulsating flow in wavy channels	1.5x increase in heat transfer coefficient at St=1.03, Re=4000	constancy of heat flux and the thermodynamic properties of HTF	15
Xu et al.	Pulsating flow + nanofluids	Microchannel heat sink	Experimental	Combined pulsating flow and nanofluids	16.5% increase in Nusselt number with square pulse at 3.5–4.5 Hz	The high price of nanofluids, uniform heat flux and Dimensionless amplitude constancy	17
Molochnikov et al.	Pulsating laminar flow	Smooth horizontal pipe	Experimental	Studied sinusoidal pulsating flow effects	Increase local Nusselt number in Stokes region at high frequencies	Using a simple horizontal pipe, laminar flow and uniform heat flux	18
Naveenkumar et al.	Steady flow	PTC	Experimental	Introduced alternating rotation of absorber tube	18% increase in outlet temperature; 39% increase in heat transfer rate	baseline steady conditions and high implementation costs	20
Cheng et al.	Steady flow	PTC	Numerical	Studied fluid type and vacuum effects on efficiency	Fluid properties and vacuum conditions impact efficiency	baseline steady conditions and no efficiency improvement	4