CAPACITY CONVERSIONS FOR SAFETY VALVES PROGRAM
安全閥流量轉換程式

1. maxima 基本程式

原始碼下載： ccfave.mac 

/*CAPACITY CONVERSIONS FOR SAFETY VALVES 安全閥流量轉換*/
/*kill(all);*/
/*單位系統*/
/* unit_system: "U.S. Customary" or "SI";*/

/*對於蒸汽
C_N = 51.5 for U.S. Customary calculations
    = 5.25 for SI calculations
*/
W_s(K,A,P):=block([CN:if unit_system = "U.S. Customary" then 51.5 else 5.25],CN*K*A*P);

/*對於空氣
C = 356 for U.S. Customary calculations
  = 27.03 for SI calculations
M = 28.97 mol/wt.
T = 520 when W a is the rated capacity (for U.S. Cus-
    tomary calculations)
  = 293 when W a is the rated capacity (for SI
    calculations)
  */

W_a(K,A,P):=block([
  C: if unit_system = "U.S. Customary" then 356.0 else 27.03,
  M: 28.97,
  T: if unit_system = "U.S. Customary" then 520.0 else 29.3],
  C*K*A*P*sqrt(M/T));

/*對於任何氣體或蒸氣 */
/*
A = ac tua l dis c harge area of the s af ety v alve ,
in. 2 (mm 2 )
C = constant for gas or vapor which is function of the
ratio of specific heats, k = c p /c v (see Figure 11-1)
K = coefficient of discharge [see UG-131(d) and
UG-131(e)]
M = molecular weight
P = (set pressure × 1.10) plus atmospheric pressure,
psia (MPa a b s )
T = absolute temperature at inlet [(°F + 460) (K)]
W = flow of any gas or vapor, lb/hr
W a = rated capacity, converted to lb/hr (kg/h) of air at
60°F (20°C), inlet temperature
W s = rated capacity, lb/hr (kg/h) of steam
*/
W(C,K,A,P,M,T):= block([], C*K*A*P*sqrt(M/T));

2. 例子

2.1. EXAMPLE 1

鑑於：安全閥具有經過認證的額定容量壓力設定為 200 psi 時，蒸汽流量為 3,020 lb/hr。問題：此閥門的洩壓能力是多少就相同壓力設定下 100°F 的 空氣而言？ 

/* EX1 */
/*
GIVEN: A safety valve bears a certified capacity rating
of 3,020 lb/hr of steam for a pressure setting of 200 psi.
PROBLEM: What is the relieving capacity of that valve
in terms of air at 100°F for the same pressure setting?
*/
/*SOLUTION:*/
batch("ccfave.mac");
/*單位系統*/
unit_system: "U.S. Customary";

/*For steam*/
W[s]:3020.0$
s1:solve(ratsubst(KAP,K*A*P,W[s]=W_s(K,A,P)),KAP)$
/*printf(true,"~&~A~&~A",ratsubst(KAP,K*A*P,W[s]=W_s(K,A,P)),s1)$*/
print("W[s]=",W[s])$
print(float(ratsubst(KAP,K*A*P,W[s]=W_s(K,A,P))))$
print(float(s1))$

C[a]:if unit_system = "U.S. Customary" then 356.0 else 27.03$
M[a]:28.97$
T[a]:460.0+100.0$
W[a]:W(C[a],K,A,P,M[a],T[a])$

print("C=", C[a])$
print("M=", M[a])$
print("T=460+100=", T[a])$
print("W[a]=",float(ratsubst(KAP,K*A*P,W[a])))$
print("=",float(ev(ratsubst(KAP,K*A*P,W[a]),s1)))$

2.2. EXAMPLE 2

鑑於：需要釋放 5,000 lb/hr 的丙烷從壓力容器經安全閥組洩壓，壓力為 P_s, psi ，入口溫度為溫度為 125°F。 問題：安全閥必須提供的總流量（lb/hr 蒸汽）是多少？

2.2.1. maxima

/*
GIVEN: It is required to relieve 5,000 lb/hr of propane
from a pressure vessel through a safety valve set to re-
lieve at a pressure of P s , psi, and with an inlet temperature
at 125°F.
PROBLEM: What total capacity in pounds of steam per
hour in safety valves must be furnished?
*/

/*SOLUTION:*/
kill(all);
/*自行下載 ccfave.mac */
batch("ccfave.mac");
/*單位系統*/
unit_system: "U.S. Customary";

/*
對於丙烷
*/
f0:W[p]=W(C,K,A,P,M,T);
/*
The value of C is not definitely known. Use the conser- value, C = 315.
*/
C[p]:315.0;
M[p]:44.09;
T[p]:460.0+125.0;
W[p]:5000.0;

f01:ev(f0,C=C[p],M=M[p],T=T[p],W[p]:W[p]);
f02:ratsubst(KAP,K*A*P,f01);

f1:float(solve(f02,KAP));

/*For steam, 對於蒸汽*/

f2:W[s]=ratsubst(KAP,K*A*P,W_s(K,A,P));

/* unit: lb/hr set to relieve at P_s,psi */
f3:ev(f2,f1);

3. 說明

  • 本文件非法規設備設計文件。
  • This document is not a regulatory equipment design document.

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