Page 375 - Defrosting for Air Source Heat Pump

372 Index

Frosting evenness coefficient (FEC) G
(Continued) Gravity force (G), 123
energy analysis, 173–175 Ground-source heat pumps (GSHPs), 1–2
energy supplies, 173, 173f
experimental cases, 165, 166t H
fin surface temperature, 167–172,
169–170f Heat exchangers, 116–117
with local drainage of melted frost, Heat pumps, 1
175–191 absorption, 1
melted frost temperature, 167–173, compression, 1
heat sources, 1–2
171f
Holographic interferometry technique, 36
refrigerant volumetric flow rate,
Horizontal heat exchangers, 116–117
167–172, 170f
Horizontal installation, 116, 117f, 118, 119f,
tube surface temperatures, 167–172,
123–124
167–168f
Hot gas bypass defrosting (HGBD), 26
multicircuit outdoor coil
Hot water spraying defrosting (HWSD)
airside surface conditions, 154, 155f,
method, 26, 27t
158, 159f
HWSD. See Hot water spraying defrosting
air temperature, 162f, 164
(HWSD) method
ASHP unit, 155–156
Hybrid heat pump systems, 2–3
COP variation, 163f, 164
Hygrosensor, 50
even frosting, control method of,
156–157
I
experimental cases, 155–157, 159t
Infrared thermometer, 36
fin surface temperatures, 163f, 164
Inlet air
refrigerant pressure drop, 159–160, 161f,
humidity, 13
162–163
preheating, 13–16
refrigerant volume flow rate, 156–157,
Inlet airflow rate, 16
159–160, 161f, 162–163
tube surface temperatures, 156–157, K
157–158f, 159–162, 160f, 162f
Frosting mechanism, 3–5 K-type thermocouples, 50–51, 119–121,
Frost-suppression measures, 12–23, 12f 229–230
air jet technique, 17
external heating source, 22–23 L
external type, 12 LGUs. See Load-generating units (LGUs)
internal type, 12 Liquid refrigerant heat transfer coefficient, 78
outdoor coil Load-generating units (LGUs), 50, 96, 118
coating treatment on fin surface, 18–19, Local drainage, of melted frost
20–21t frosting evenness coefficient with
fin and tube geometry adjustment, 17–18 airside surface conditions of outdoor
fin-type adjustment, 18 coil, 178–179, 179f
increasing inlet airflow rate, 16 defrosting durations, 188–189, 188t,
preheating inlet air, 13–16 190f
reducing inlet air humidity, 13 defrosting efficiency, 189, 190f
solid and liquid desiccants for, 13, 14–15t downward-flowing melted frost, 176,
two-stage technique, 22 177t
ultrasonic vibration technique, 16–17 energy analysis, 188–191, 189t, 190f
vapor-injection technique, 19–22 experimental cases, 177–178, 178t