Page 378 - Defrosting for Air Source Heat Pump
P. 378
Index 375
T outdoor coil airside surface conditions,
Technoeconomic performances 262–263, 262–263f
defrosting duration, 303 refrigerant pressure difference, fluctuation
defrosting efficiency, 303 of, 267f
refrigerant volumetric flow rate, fluctuation
energy performance improvement, 304
frosting and defrosting state of, 266f
assumptions, 304 trial-and-error manual adjustments, 260
hot refrigerant tube and fins, 303 Two semiempirical models, 73–85, 74t
multicircuit outdoor coil, 303 airside of three-circuit outdoor coil, 73–74,
novel RCD method, 303–304 73f
refrigeration adjustment valve, assumptions and calculation conditions,
influence of 75–76
cooling assumptions, 312 computational algorithm, 84, 85f
defrosting assumptions, 311 defrosting process, 74
defrosting operations, airside surface development of, 75–85
conditions of, 308–309, 308f energy used from refrigerant, 91–92, 93f
economic analysis model, 317 experimental validation, 86–90
economic analysis process, 307 frost melting without water flowing away
first costs, 312 from circuit, 79–81, 80f
flow chart of methodology, 305f frost melting with water flowing away from
frosting assumptions, 310 circuit, 81–82
frosting/defrosting cycle, 306 limitations, 94
frosting operations, airside surface mass and energy flows in defrosting
conditions of, 307–308, 307f stages, 80f,84f
fundamental assumptions, 309 mass of melted frost, 91–92, 93f
installation of valves and trays, 305–306 melted frost temperatures, 87–90, 87–89f
performance parameters, 305, 306t melted water temperature, 91–92, 92f
refrigerant distribution, 307 model extrapolation, 90–91
running cost, 313 preheating, 76–79
swing-type compressor, 305 refrigerant mass flow rate, 90–91, 91f
three-circuit outdoor coil, 305–306 refrigerant temperature, 90–91, 90f
and water-collecting tray, 324–340 thermal resistance of refrigerant, 91–92,
water-collecting trays, 305–306 92f
Thermal conductivity, 78–79 tube surface temperatures, 86–87, 86f,88f
Thermal energy storage (TES) system, 28 uses, 94
Thermal expansion valve (TEV), 28 water-collecting cylinder, 83–84, 85f
Three-circuit outdoor coil, 116, 119f water-collecting trays, 73–74, 83–84, 85f
Time-based defrosting initiation control water layer vaporizing, 82–83
strategy, 258, 344–345 Two-stage technique, 22
DX A/C system, 260–261
energy supply and, 271f U
flow chart of procedure, 261f Ultrasonic vibration technique, 16–17
fluctuation of tube surface temperature, Uneven defrosting, 303, 343
264–265f for ASHP unit, 95–110
frost accumulation, 260, 272f airside of three-circuit outdoor coil, 98,
indoor coil air temperature difference, 98f
fluctuation of, 269f assumptions, 102–103
melted frost, fluctuation of, 266f defrosting durations, 104, 104t