### 『Chromium plating＆Heat exchanger 』

• Heat exchangers made of plastics such as fluoroplastics include tube bundle immersion, column tube and spiral tube, which can be used for heating and……

#### Heat transfer

##### Calculation of heat transfer area of fluoroplastic heat exchanger

Heat exchangers made of plastics such as fluoroplastics include tube bundle immersion, column tube, spiral tube, etc., which can be used for both heating and cooling.The calculation method of heat transfer area is as follows:

1.Calculation method of heat transfer area
Temperature rise
(1) Heat exchange Q (-W.h)
Q=1.16 β.γ c.V (T2-T1)
β-heat loss coefficient (1.05 ~ 1.3) γ-liquid density (kg/L) c-liquid specific heat (kcal/kg)
v-liquid volume (L) T1-liquid initial temperature (℃) T2-liquid process temperature (i.e.process temperature)
(2) heat exchange area S (-m2)
S=Q/(Δ T.κ.h)
Q-heat exchange (W.h) h-heat exchange duration (h) κ-heat transfer coefficient (150 ~ 350 W/m2.℃)
Δ T-average temperature (℃)
Δ T is calculated as follows:
-if the heat transfer is latent heat (e.g.steam)
Δ T ≈ (Ty-Tx)/Ln [(Tz-Tx)/(Tz-Ty)]
where Tz-saturated steam temperature (℃)
Tx-initial liquid temperature (℃) Ty-liquid process temperature (℃)
-if the heat transfer is sensible heat (e.g.hot water)
Δ T ≈ [(T1-Ty)-(T2-Tx)]/Ln [(T1-Ty)/(T2-Tx)]
T1-inlet temperature (℃) T2-outlet temperature (℃)
Tx-initial liquid temperature (℃) Ty-liquid process Temperature (℃)

Cooling
(1) Calculating heat exchange q (-W)
q=β.V.I
β-additional coefficient (1.1 ~ 1.3) V-working voltage (v) I-working current (a)
(2)  Calculating heat exchange area s (-m2)
s=q/(Δ T.kappa)
q-heat exchange (W) κ-heat exchange coefficient Δ T-average temperature (℃)
Δ T
-If direct cooling in tube bundle tank
Δ T ≈ ( T2-T1)/Ln [(T-T1)/(T-T2)]
where T-process temperature
T1-refrigerant inlet temperature
T1-refrigerant inlet temperature
T2-refrigerant inlet temperature
T2 is a natural logarithm
T2 mainly depends on the flow rate of circulating pump and Interrelation of heat exchange

2.Check calculation of heat exchange area
S=d × 3.14 × n × l × m
where d-nominal pipe diameter of plastic pipe (m) L-average length of plastic pipe (m)
n-number of plastic pipes in each heat exchanger group m-number of heat exchanger groups

3.Explain that
heat transfer coefficient depends not only on heat transfer mode, heat exchanger material and tube wall thickness of material, but also on many factors such as solution state (such as stirring or flow speed).Generally, the upper limit is desirable for steam heating, and the lower limit is desirable for hot water heating or refrigerant cooling.