Absorption Refrigerator Desorber Design for High COP

Overview of Technical Issues:

The desorber's heat transfer surface insufficiently transmits thermal energy to the refrigerant-absorbent solution, requiring excessive heat input from the source to achieve adequate refrigerant separation, which directly reduces the coefficient of performance (COP) of the absorption refrigeration system; the goal is to optimize the desorber design to maximize heat transfer efficiency and achieve high COP.

Solution directions generated for this problem

Problem Direction 1 :

ImproveHeat transfer surface area
VS
ConstraintDesorber volume

Inspiration 1 : Cross-domain reference

Application Principle: #17 Another dimension
Cross-domain applicability Assess applicability
Compact head mounted display system
Innovative Solution Refine solution

Helical multi-layer tube bundle desorber with vertical stacking architecture

Vertical stacking of helical tube layers maximizes area within fixed envelope
How to solve :
  • Install 3–5 concentric helical tube layers vertically inside existing cylindrical shell, each layer offset 60° azimuthally to eliminate dead zones and maximize packing density within unchanged outer diameter
  • Use stainless steel 316L tubes (OD 12mm, wall 0.8mm, pitch 25mm) with thermal conductivity ≥16 W/(m·K), helical winding on mandrels then TIG-welded to top/bottom manifolds, ensuring leak rate <10⁻⁶ mbar·L/s
  • Implement counter-flow vertical solution distribution: dilute solution enters top manifold at 85–95°C, flows downward through helical passages while heat source fluid flows upward in shell side at 110–130°C, achieving LMTD ≥25°C and heat transfer coefficient ≥450 W/(m²·K)
Expected Effect : Heat transfer area +180–220% within same volume; COP improvement 18–24%; desorber height increase <8%
Risk Control :
  • Helical tube pitch uniformity tolerance ±0.5mm critical for flow distribution
  • manifold weld joint integrity under thermal cycling
  • solution maldistribution risk in multi-layer parallel paths requiring flow balancing orifices

Problem Direction 2 :

ImproveHeat transfer coefficient
VS
ConstraintManufacturing complexity

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Apparatus for heating smokable material
Innovative Solution Refine solution

Nanofluid-enhanced desorber with phase-change thermal buffer

Use nanofluid and phase-change material to boost heat transfer without complex geometry
How to solve :
  • Replace conventional heat transfer fluid with Al₂O₃ or CuO nanofluid (0.5–2 vol%) on heat source side, enhancing thermal conductivity by 15–25% without modifying desorber structure
  • Integrate phase-change material (PCM) jacket (paraffin wax, melting point 60–80°C, latent heat ≥200 kJ/kg) around desorber shell to buffer heat input and smooth temperature fluctuations
  • Install simple ultrasonic transducer (20–40 kHz, 50–100 W) at desorber inlet to agitate solution boundary layer, increasing convective heat transfer coefficient by 20–30%
Expected Effect : Heat transfer coefficient +35–50%, COP improvement 12–18%, no structural redesign
Risk Control :
  • nanofluid stability and sedimentation over time
  • PCM thermal cycling degradation and leakage
  • ultrasonic transducer fouling and power consumption

Problem Direction 3 :

ImproveThermal efficiency
VS
ConstraintManufacturing complexity

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out
Cross-domain applicability Assess applicability
Architecture for a three-dimensional nonvolatile memory with vertical bit lines
Innovative Solution Refine solution

Solution-side heat recovery loop for desorber thermal efficiency enhancement

Extract waste heat from desorber outlet streams and reuse it to preheat incoming solution
How to solve :
  • Install a tube-in-tube heat exchanger externally where hot concentrated solution (85–95°C) exiting the desorber flows through the inner tube and preheats incoming dilute solution (40–50°C) in the outer annulus, recovering 15–25% of sensible heat without modifying desorber internals
  • Use standard stainless steel 304 seamless tubes (inner Φ25×1.5mm, outer Φ38×2mm, length 1.2–1.8m) with countercurrent flow arrangement, achieving heat recovery effectiveness ε≥0.6 and pressure drop <5kPa per side
  • Implement inline temperature monitoring at four points (inlet/outlet of both streams) with ±1°C accuracy thermocouples, and verify heat recovery rate weekly by measuring ΔT and mass flow rate to maintain COP improvement within ±3% of target
Expected Effect : COP increase 12–18%, payback period <18 months, no desorber redesign required
Risk Control :
  • fouling in heat exchanger reducing effectiveness over time
  • thermal expansion mismatch causing tube joint leakage
  • flow imbalance between solution streams degrading heat recovery
Patsnap Eureka Solution