Absorption Refrigerator for Natural Gas Processing Plant

Overview of Technical Issues:

In absorption refrigerators for natural gas processing plants, the absorber vessel often exhibits insufficient heat rejection capability when absorbing refrigerant vapor back into solution—the generated absorption heat cannot be adequately removed to the cooling medium, causing the absorption rate to decrease and the overall system cooling capacity to fall below the required level for maintaining natural gas processing temperatures, reducing throughput and separation efficiency.

Solution directions generated for this problem

Problem Direction 1 :

ImproveHeat transfer area
VS
ConstraintVessel volume

Inspiration 1 : Cross-domain reference

Application Principle: #7 Nested doll (Nesting)
Cross-domain applicability Assess applicability
Flow reactor
Innovative Solution Refine solution

Concentric helical coil absorber with nested tube bundles

Install nested tube-in-tube heat exchanger within absorber vessel
How to solve :
  • Deploy concentric triple-layer helical coil bundles where inner coil (Ø25mm), middle coil (Ø50mm), and outer coil (Ø80mm) nest within each other, multiplying effective heat transfer area by 2.8× within the same vessel diameter
  • fabricate coils from copper-clad carbon steel composite tubes (thermal conductivity ≥200 W/(m·K), wall thickness 2.0±0.1mm) with helical pitch 150–200mm to ensure uniform solution distribution and coolant flow
  • connect each coil layer to independent coolant circuits with flow rates 8–12 m³/h per layer, maintaining tube-side velocity 1.2–1.8 m/s and solution-side Reynolds number >5000 for turbulent heat transfer coefficient 420–480 W/(m²·K)
Expected Effect : Area +165%, volume unchanged, heat rejection +58%, absorption capacity restored to 95–98% design
Risk Control :
  • coil pitch tolerance exceeding ±5mm causing flow maldistribution
  • welding thermal deformation >2mm at coil junctions
  • fouling accumulation between nested layers reducing clearance below 8mm

Problem Direction 2 :

ImproveOverall heat transfer coefficient
VS
ConstraintInternal structure complexity

Inspiration 1 : Cross-domain reference

Application Principle: #28 Mechanics substitution (Replace mechanical system)
Cross-domain applicability Assess applicability
Well fracturing systems with electrical motors and methods of use
Innovative Solution Refine solution

Ultrasonic acoustic streaming enhancement for absorber heat transfer

Replace mechanical enhancement with ultrasonic field
How to solve :
  • Mount piezoelectric ultrasonic transducers (28–40 kHz, 1.5–2.5 W/cm² intensity) on absorber shell exterior at 300–400 mm vertical spacing to generate acoustic streaming in solution boundary layer without internal modifications
  • Configure transducers in phased array mode with 120° angular offset to create rotating acoustic pressure field that disrupts thermal boundary layer, enhancing convective heat transfer coefficient by 60–80% to target 400–500 W/m²·K range
  • Implement PLC-controlled power modulation (duty cycle 70–85%) synchronized with absorption load—monitor solution temperature via RTD sensors (±0.2°C accuracy) and adjust ultrasonic intensity to maintain heat transfer coefficient ≥400 W/m²·K while preventing cavitation damage (pressure amplitude <150 kPa)
Expected Effect : Heat transfer coefficient +70% to 450 W/m²·K; absorption capacity recovery 20%; zero internal complexity addition; retrofit-compatible
Risk Control :
  • transducer coupling efficiency degradation over time
  • cavitation-induced surface erosion if intensity exceeds threshold
  • fouling layer attenuates acoustic transmission

Problem Direction 3 :

ImproveTemperature driving force
VS
ConstraintVessel volume

Inspiration 1 : Cross-domain reference

Application Principle: #24 Intermediary (Mediator)
Cross-domain applicability Assess applicability
Battery module having excellent radiation property and medium to large sized battery pack
Innovative Solution Refine solution

Closed-loop intermediate thermal fluid system for enhanced temperature driving force

Use intermediate thermal fluid loop to decouple driving force from vessel size
How to solve :
  • Install a closed-loop glycol-water circuit (30-40% glycol) between absorber tubes and final cooling water, operating at 5-8°C below current coolant temperature to achieve 15-20°C solution-to-fluid ΔT without vessel modification
  • Deploy a compact external plate heat exchanger (316L stainless steel, brazed plate type, 0.6mm channel spacing) sized at 15-20 m² to transfer heat from intermediate fluid to cooling water, located in adjacent available space without expanding absorber footprint
  • Circulate intermediate fluid at 1.2-1.5× absorber cooling flow rate using a variable-speed centrifugal pump (3-5 kW) with PID control maintaining fluid supply temperature at -2 to 0°C, ensuring consistent 15-20°C driving force across all operating loads
Expected Effect : ΔT increased from 8-12°C to 15-20°C; heat rejection capacity +60-75%; absorption rate restored to design; zero absorber vessel modification
Risk Control :
  • glycol concentration drift affecting thermal properties
  • intermediate loop fouling reducing heat transfer
  • pump cavitation at low fluid temperature

Problem Direction 4 :

ImproveHeat rejection rate
VS
ConstraintInternal structure complexity

Inspiration 1 : Cross-domain reference

Application Principle: #25 Self-service
Cross-domain applicability Assess applicability
Braking devices and methods
Innovative Solution Refine solution

Solution-driven turbulence generation for enhanced heat rejection without added internals

Harness solution flow momentum for self-induced turbulence
How to solve :
  • Design tangential inlet nozzles (4–6 units at 15° angle) that inject rich solution at 2.5–3.5 m/s to create helical swirl flow throughout absorber volume, generating turbulence intensity >0.15 without internal structures
  • Install flow redistribution rings (3–4 levels, open-area ratio 65–75%) as non-intrusive guides to sustain swirl decay length >8 vessel diameters, maintaining Reynolds number >15,000 in heat transfer zones
  • Optimize solution mass flux distribution via CFD-validated nozzle sizing (diameter 50–80mm) to achieve uniform wall-wetting and 25–35% heat transfer coefficient enhancement, targeting 350–420 W/m²·K without adding fins or multi-pass arrangements
Expected Effect : Heat rejection rate +28%, structure complexity unchanged, fabrication cost −15%
Risk Control :
  • nozzle erosion from particle-laden solution
  • swirl pattern instability under turndown
  • flow maldistribution at low loads

Problem Direction 5 :

ImproveHeat transfer area
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Aerosol delivery system
Innovative Solution Refine solution

Dual-zone segmented absorber bundle retrofit

Split duty by vessel height
How to solve :
  • Install dense upper microtube bundle in top 35-45% where absorption heat peaks, keep lower zone sparse smooth tubes
  • Use 316L SS tubes OD 12-16 mm, pitch 1.25-1.4D upper and 1.8-2.2D lower, with redistributor trays every 0.8-1.2 m
  • Control film wetting and QC: liquid maldistribution <±10%, tube spacing tolerance ±1.0 mm, hydrotest 1.3× design pressure, helium leak <1×10⁻⁶ mbar·L/s
Expected Effect : Area +45-60%, U overall 320-420 W/m²·K, absorber duty +18-25%, vessel OD unchanged, cooling capacity restored to 95-100% of design, 10-15% better than uniform smooth-tube retrofit
Risk Control :
  • upper-zone fouling risk
  • liquid maldistribution at redistributors
  • bundle vibration under gas surge
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