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raw · papers · ingested 2026-07-02

Evaluation of Low-Pressure Flooded Evaporator Performance for Adsorption Chillers (Thimmaiah, Bahrami et al., Energy 2017)

confidence: high

Source: https://www.sfu.ca/~mbahrami/pdf/2017/P.%20C.%20Thimmaiah,%20A.%20Sharafian,%20M.%20Rouhani,%20W.%20Huttema,%20M.%20Bahrami%20-%20Evaluation%20of%20low-pressure%20flooded%20evaporator%20for%20adsorption%20chillers.pdf

Source: Thimmaiah, Sharafian, Rouhani, Huttema, Bahrami, Energy 122 (2017), SFU. Peer-reviewed, full PDF. Credibility: High — exact specs + measured numbers.

Key points

  • Pressure regime: 0.76–2.34 kPa to evaporate 3–20 °C (1.22 kPa → boils at 10 °C).
  • Hydrostatic pitfall: P = Pvap + ρgH; 20 cm depth adds 3.2 kPa → local Tsat 25 °C → no cooling. Keep the pool shallow.
  • Buildable design: 12 finned copper tubes (1/2” OD, 26 fpi, 1.5 mm fins) in a shallow pool, vessel 38.1×11.4 cm; chilled water pumped through the bores, refrigerant evaporates off the fins.
  • Charge rule: H* = 0.8 (refrigerant height = 80% of tube diameter). Higher → hydrostatic penalty; lower → capillary fails to wet fins.
  • Measured: 135→440 W cooling (chilled inlet 5→20 °C); U 790→1670 W/m²K; 73% of resistance is convective (tube surface matters, not wall).
  • Enhancements: twisted-tape +12%, Z-turbulators +58%, porous-copper coating U×1.4/SCP+48%.
  • Degas the water (evacuate) to remove non-condensables or performance collapses.
  • Table 1 = 9 buildable LP evaporators (flooded/falling-film/capillary) with U values.