Complete this table for refrigerant-134a: T,^∘C P, kPa u, kJ / kg Phase descripti

Complete this table for refrigerant-134a: T,^∘C P,...

Key Concepts

Thermodynamic Property Tables

These tables compile experimentally and theoretically determined values of state properties such as temperature, pressure, and internal energy. They are used to evaluate the conditions of a substance and are essential for performing calculations in thermodynamic and refrigeration analyses by providing standard reference data.

Phase Equilibrium and Saturation

Phase equilibrium occurs when a substance is in a state where multiple phases, typically liquid and vapor, coexist at a specific temperature and pressure known as the saturation conditions. Understanding saturation is critical, as it dictates the energy and work interactions during phase change processes in thermodynamic cycles.

Refrigerants

Refrigerants are working fluids used in heat transfer systems like air conditioners and refrigerators. Their unique thermodynamic properties, including phase behavior and energy transfer characteristics, enable them to absorb and release heat efficiently during evaporation and condensation processes, which is vital for system performance.

Interpolation in Thermodynamic Calculations

Interpolation is a mathematical technique used to estimate values between data points in property tables. This method allows engineers to calculate approximate thermodynamic properties when the exact value is not tabulated, thereby ensuring accurate analysis and design of refrigeration and other thermal systems.

Transcript

00:01 In this problem we have to complete this given table for reference 134a.

00:11 Now comes to part a.

00:15 So here we have given t equal 20 degrees celsius and u equal 95 kilojou per kg.

00:29 Now we have to find out the pressure and the phase description.

00:36 Now, as we see that there is only temperature and internal energy are given, so we do not know that which table to use to determine the missing properties.

00:48 As we have no cues to whether we have saturated mixture, compressed liquid or superheated vapor.

00:59 So this can be determined from the internal energy of saturated liquid and internal energy of saturated vapor.

01:08 Choose the table saturated rafidine 134a at t equal 20 degrees celsius.

01:18 So at t equal 20 degrees celsius, uf equals to 78 .86 kilojoule per kg and u g equals to 241 .0 .0 per kg.

01:53 Now here the given value of u that is 95 kilojoules per kg is between uf and u g therefore we have saturated liquid wrapper mixture and the pressure at given temperature is given by p equal p saturated at 20 degrees celsius equals to 572 .072 .0 .07 so here pressure is actually 572 .07.

02:51 And talking about the phase description.

02:59 So this is actually a two -phase mixture.

03:13 In this, there is a saturated liquid vapor mixture.

03:18 Now comes to part b.

03:22 Here we have given the phase is saturated liquid and temperature is p equal to minus 12 degree.

03:32 Now from the saturated refrigerant 134a temperature table, we can obtain the values of temperature temperature and internal allergy called saturated liquid at t equal minus 12 degrees celsius.

03:56 So here from table we get p equal p saturated, at minus 12 degrees celsius equals to 185 .37 kilo pascal.

04:16 So this is the value of p.

04:20 And now comes to intended energy, so u is equal to uf at minus 12 degrees celsius...

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