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Calculation method and formula of plate heat exchanger selection
1) Find the heat load Q
Q = G. ρ. CP. Δt
+ ~ + ~, X6 C% Y
(2) Find the inlet and outlet temperature of the hot and cold fluid 3 O% d (k; a4 ~ (J! Z
6 B1 O0 R # E (k% ^: _5 E4 H
t2 = t1 + Q / G. ρ.
(3) Flow of hot and cold fluid 4 c. M7 S $ K5 @) D / v
% C5 I3 o8 j: b
(T2-t1 9 i5 x I,? 'N
9 i1 A7 ~ 2 R; z4 M0 J1 c "Q $ w
(4) Find the average temperature difference Δtm
!! R6 S'c9? _% N / y (U6 f (B: F
Δtm = (T1-t2)-(T2-t1) / In (T1-t2) / (T2-t1) or Δtm = (T1-t2) + (T2-t1) / 2
(5) Select the plate type
4 k "V" ^ 'G $ N & A K
If all the plate types are selected, the result analysis is performed.
9 t'W, _) t0 r- v # f + j) V6 V
(6) From the range of K values, calculate the range of plate number Nmin, Nmax
Nmin = Q / Kmax. Δtm. F P. β '^; u / K &? & H8 M1 s
) @ (I0 s5 D; K) N4 K6 E + q V3 Q
Nmax = Q / Kmin. Δtm. F P. β
(7) Take the number of plates N (Nmin≤N≤Nmax)% i'x # n + Y0 C
If N has reached Nmax, do (5).
/ i $ R, \ & m & [% j Y; Q & A
(8) Take the process combination form of N. If the combination form is taken, do (7).
(9) Find Re, Nu 8 ^% k & R: R8 Y (m (A, Q
Re = W. de / ν5 d0 W: v8 e / k + d &] $ r
Nu = a1. Rea2. Pra3
* W'J4 V; v3 L! f) M8 X
(10) Find a, K heat transfer area F 9 d (s9 ?! z3 ~ 5 F
a = Nu. λ / de + W- G6] / y / n;?
: B "Y. H5 v.k * |: ^ 3 F
K = 1/1 / ah + 1 / ac + γc + γc + δ / λ0
'f7 | 3 e! l / R (O “m- N9 E & g
F = Q / K. Δtm. β % n4 Y # h $ h) j Y + U9 Y) Q
3 U + ^ / [# s'E6 S
(11) Find the required number of plates NN from the heat transfer area F
!! G # Y) N; x6 d2 I (@
No = F / Fp + 2, A2 \ 'l% u *} $ d5 p
# I- @ 9 e. years
(12) If N <NN, do (8).
(13) Find the pressure drop Δp
Eu = a4. Rea5
% Q! u $ [5? 7 N1 K7 h2 R / v2 d
Δp = Eu. ρ. W2. ф
(14) If Δp> Δ allows, do (8); 1 h # ^ * A! u% n / M * E
& M + m5 @ & | 5 [#z ([! V
If Δp≤Δ is allowed, record the result and do (8). : L / R; j8 o (B & f% L
Note: 1. (1), (2), (3) Calculate according to known conditions. {"X, d,], C, @
2. When T1-t2 = T2-t1, Δtm = (T1-t2) + (T2-t1) / 2 8 Q. \ '`/ s'b
6 |; h4 T; x * h $ \
3. The correction coefficient β is generally 0.7 to 0.9. 1 D: U m $ n) a
4. Pressure drop correction coefficient ф, single process ф degree = 1 ~ 1.2, two processes, three processes ф = 1.8 to 2.0, and four processes ф = 2.6 to 2.8.
5.a1, a2, a3, a4, and a5 are constant coefficients.