CN103377311A - Heat economy analytical method for cooling, heating and power combination generation system - Google Patents

Abstract

The invention relates to a heat economy analytical method for a cooling, heating and power combination generation system. The method is mainly used for researching an expression formula of economy exergy efficiency which elaborates the difference between input energy and output energy on the nature in the system from the perspective of exergy and analyzes the difference from the perspective of economy such as power price, cooling price and heating price. The system economy is reflected to some extent, and the method is a reasonable evaluation method at present.

Description

A kind of method of analyzing thermal of cogeneration cooling heating system

Technical field

The invention belongs to technical field of power generation, especially the thermal power generation field.

Background technology

The second law of thermodynamics

(exergy): is the general designation of energy availability, available energy, available energy, and heat can be expressed as:

$E_{x_Q}=\underset{\left(Q\right)}{\∫}(1-\frac{T_0}{T})\mathrm{\δQ}---\left(1.3\right)$

Wherein: T is heat source temperature, ℃; T ₀Be environment temperature, ℃; Q is the heat that absorbs from thermal source, j.Cold can be expressed as:

$E_{x_{Q0}}=T_0\underset{\left(Q_0\right)}{\∫}\frac{\mathrm{\δQ}}{T}-Q---\left(1.4\right)$

Wherein: T is system temperature, ℃; T ₀Be environment temperature, ℃; Q is the cold that absorbs from low-temperature receiver, j.

The Carlow circulation

Desirable Carlow circulation namely passes to low-temperature receiver to the heat of thermal source through certain process, as shown in Figure 1.

According to first law of thermodynamics thermal efficiency of cycle η _t:

${\mathrm{\η}}_t=1-\frac{q_2}{q_1}---\left(1.5\right)$

Carlow thermal efficiency of cycle η _Tc:

${\mathrm{\η}}_{t,c}=1-\frac{T_2}{T_1}---\left(1.6\right)$

Wherein: T ₁Be heat source temperature, ℃; T ₂Be sink temperature, ℃; q ₁Be the heat that absorbs from thermal source, j; q ₂For to low-temperature receiver liberated heat, j.

The circulation of contrary Carlow

Desirable contrary Carlow circulation namely passes to thermal source to the heat of low-temperature receiver through certain process, as shown in Figure 1.The circulation of contrary Carlow is as refrigeration cycle, its coefficient of refrigerating performance ε _c:

${\mathrm{\ϵ}}_c=\frac{T_2}{T_1-T_2}---\left(1.7\right)$

The circulation of contrary Carlow is as heating circulation, its coefficient of heat supply ε _g:

${\mathrm{\ϵ}}_g=\frac{T_1}{T_1-T_2}---\left(1.8\right)$

Wherein: T ₁Be heat source temperature, ℃; T ₂Be sink temperature, ℃;

Summary of the invention

The thermodynamic principles of cogeneration cooling heating system

The economic efficiency analysis of thermoelectric cold system

The basic ideas of analyzing are: set up the physical model of genset, heating equipment and refrigeration unit according to the composition of system, determine respectively the total amount of fuel of generated energy, heating capacity, refrigerating capacity and the system consumption of genset.Analysis load value separately accounts for the ratio of wastage in bulk or weight, and last certain parameter that changes in the situation that other amounts remain unchanged is wherein analyzed it to the impact of system effectiveness.

System efficiency eta ^[47]:

$\mathrm{\η}=\frac{(\mathrm{\κ}{N}_e+\mathrm{\α}{Q}_c+\mathrm{\β}{Q}_h)}{(G_0\·H_0)}---\left(1.9\right)$

G ₀, H ₀Respectively the consumption m of fuel ³And low heat value, kj/m ³N _e, Q _c, Q _hRepresent respectively generated energy, refrigerating capacity and heating capacity, kw; κ, α, β represent respectively the proportionate relationship between electric weight, cold, heat and the electric weight.When κ, α, β represented respectively the ratio of electricity price, cold valency, caloric value and electricity price, η just represented the business efficiency of system.If introduce again the concept of in conjunction with (1.3) formula and (1.4) formula, variable being changed to of (1.9) formula (1.10) formula then, expression be exactly the economic efficient of system.

${\mathrm{\η}}_E=\frac{(\mathrm{\κ}{E}_{N_e}+\mathrm{\α}{E}_{Q_c}+\mathrm{\β}{E}_{Q_h})}{E_{G_0\·H_0}}---\left(1.10\right)$

Fuel,

Represent respectively electric weight, cold and heat, unit is j.

Suppose to represent fuel with effective consumption and the low heat value of fuel, the formula of economic efficient can further be expressed as η _E:

${\mathrm{\η}}_E=\frac{(\mathrm{\κ}{N}_e+\mathrm{\α}\frac{(T_0-T_2)}{T_2}{Q}_c+\mathrm{\β}\frac{(T_1-T_0)}{T_1}{Q}_h)}{G_0\·H_0}---\left(1.11\right)$

T ₁Heat source temperature, T ₂System temperature, T ₀Environment temperature, unit is ℃; G ₀, H ₀Respectively the consumption m of fuel ³And low heat value, kj/m ³N _e, Q _c, Q _hRepresent respectively generated energy, refrigerating capacity and heating capacity, unit is kw; κ, α, β represent respectively the ratio of electricity price, cold valency, caloric value and electricity price.

Formula (1.11) is the expression formula of our the economic efficient that will study, economic efficient has not only been set forth the difference on matter of input and output energy the system from the angle of, also analyze from the angle of the economy such as electricity price, cold valency and caloric value, the economy that has reflected to a certain extent system is present more rational a kind of evaluation method.

The principal element that can find out the economic efficient of impact from formula has: 1. building loading; Be the generation load N of system _e, refrigeration duty Q _c, thermal load Q _h2. the ratio of electricity price, cold valency and caloric value; Be weighting coefficient κ, α, the β value of energy front.3. heat source temperature T ₁, system temperature T ₂, environment temperature T ₀

: (exergy) Word-formation method: 3db2alt+x

Economic efficient: ${\mathrm{\η}}_E=\frac{(\mathrm{\κ}{N}_e+\mathrm{\α}\frac{(T_0-T_2)}{T_2}{Q}_c+\mathrm{\β}\frac{(T_1-T_0)}{T_1}{Q}_h)}{G_0\·H_0}$

Description of drawings

The p-v figure of Fig. 1 Carlow circulation and T-s figure

The p-v figure of Fig. 2 contrary Carlow circulation and T-s figure.

Claims (2)

1. the method for analyzing thermal of a cogeneration cooling heating system, it is characterized in that: the expression formula of the economic efficient that the present invention will study, economic efficient has not only been set forth the difference on matter of input and output energy the system from the angle of, also analyze from the angle of the economy such as electricity price, cold valency and caloric value, reflected to a certain extent the economy of system.

2. method of analyzing thermal claimed in claim 1 is characterized in that, the analysis that relates generally to three key elements is building loading 1.; Be the generation load N of system _e, refrigeration duty Q _c, thermal load Q _h2. the ratio of electricity price, cold valency and caloric value; Be weighting coefficient κ, α, the β value of energy front.3. heat source temperature T ₁, system temperature T ₂, environment temperature T ₀

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