Refrigeration Definition and 78 Threads

Hi all, I'm doing some research on vapour absorption cycle machines, mainly water ammonia refrigerators. I've got a few questions. 1. What is the role of the water absorber? ie why do we need the water? 2. In the absorber we have a water ammonia solution. Is the ammonia a gas in the solution...

If I orient my refrigerator such that the condenser coils at the back are facing a glass door (least insulation in room, cold outdoors) will CP increase? CP=Qc/(Qh-Qc) so Qh-Qc will be smaller thus CP larger. Could this damage refrigerator?

Greetings! I'm a recent ME grad and I'm trying to design a refrigeration system for the first time. I understand most of the theory and calculations (I guess not, cause I wouldn't be here otherwise), but I'm having difficulty applying it to the real world. Homework problems in college often...

Can efficiency be larger than 100%? I have double checked the values of enthalpy of point 1,2,3 from R-22 tables. And I obtained enthalpy of point 4 from the work done given. Thank you.

Is it the lower the boiling point the better? As room pressure and temperature already can change the phase without working at vacuum? And the higher critical point means it is hard to reach super critical phase? But there is transcritical CO2 cycle, which the critical point is so low, and...

How to get h3 = 111.37? According to table a-13, sat temp@1.2MPa = 46.29oC, and T3 is lower than that. So the refrigerant should be totally in liquid state, and heat capacity should be used instead. However, from textbook, no heat capacity is given from table. If graph of A14 is used, at 1.2MPa...

The refrigeration process is used in air conditioning to dehumidify and control temperatures in homes and buildings. The heating industry preceded the air conditioning business and many evaporator coils were placed on top of furnaces to create split systems and utilize existing ductwork. The...

My question is generated by a an unsuccessful attempt to construct the einstein system with limited knowledge. The first part the counter flow of different gasses (See attachment No1) The main part is the simplified Einstein is what prevents counter flow in this system. I think that perhaps...

WHERE is the refrigerant stored in the refrigeration system when the system is in OFF and in WHAT state Gas or Liquid ?

I've been trying to understand how dilution refrigerators work and inbetween intermediate steps, between different temperature points, I see capillaries here and there under the name of impedances. After some googling, I somewhat convinced myself that it's to build up pressure before and after...

Hello, Can anyone tell me please the P,V,h, etc, ie all parameters for an ideal refrigeration cycle? I am not sure which points of the cycle have same pressure, temperature, etc. Thanks!

Homework Statement The temperature of a 12-oz (0.354-L) can of soft drink is reduced from 20 to 5 ºC by a refrigeration cycle. The cycle receives energy by heat transfer from the soft drink and discharges energy by heat transfer at 20 ºC to the surroundings. There are no other heat transfers...

I know that the Cascade Refrigeration Systems are more efficient than the normal Refrigeration Systems, but I still don't know why?

water is flowing in the closed looped pipe equipped with preheater. there are pressure and temperature gauges before the preheater and after the preheater. which pressure gauge should i use to know whether the outlet preheater temperature has reached the saturation temperature?

All of us have some idea about cavitation process. I want to know how much cavitation can cause problem in the absorption refrigeration process.

It appears very non intuitive to me seeing TS diagram of vapour compression system; Area under the curve increases. But how seriously how higher evaporator temperature will lead to higher refrigeration effect. Refrigeration effect means lower temperature.

I have a brayton refrigeration cycle with a regeneator same as the picture below only with irreversible regenrator, compressor and turbine (And different values). The given in my problem are: Ti=0 C, T3= 35 C, T5= -80 C, mass flow rate m= 0.4 kg/s Turbine efficiency Et=0.85, Compressor...

Suppose there is a test chamber containing liquid nitrogen. The container is insulated and only a small opening is there so that chamber is exposed to atmospheric condition. As the saturation temperature of liquid nitrogen is -196 degree Celsius at 1 atm pressure. chamber will remain at -196...

Can we really reduce the compressor work by adding phase change material in evaporator. theoretically, it looks that it'll work but still confusion remains...

Homework Statement Cooling of a food from 293K (20 ⁰C), freezing it at 272K (-1⁰C), and further cooling to 253K (-20 ⁰C); using cooling water rising in temperature from 293K (20 ⁰C) to 303K (30 ⁰C) to accept heat. The specific heat of the unfrozen food is taken as 3.2 kJ/kg K, that of the...

Hi there, I just sign up today. I'm curious to know about the energy added/released in a Carnot Refrigeration Cycle. Let's say the problem is like this: A Carnot Refrigerator used refrigerant-134a as the working fluid. During the heat addition process, a percentage of mass of the refrigerant...

The refrigeration cycle is often likened to a reverse Carnot cycle. I pretty much understand the Carnot cycle, but in relating it to a household refrigerator, I am lost. Where is the adiabatic compression done on the machine (inside vs. outside) , and where is the adiabatic expansion? How is...

Hello Guys, This is my first time posting here - just wondering if anyone has some insight on a project that I am working on. I want to be able to temperature control an insulated shoe box sized volume at ~5 degrees Celsius for about 20 minutes. The main constraints are that I would need the...

Considering two thermal energy reservoirs, one at a higher temperature of TH compared to the other at TL, if we operate a reversible refrigeration cycle between the reservoirs then its coefficient of performance is given by, COPR,rev=TL/TH-TL This is the basically the maximum COP a...

Hi, I am currently trying to model a water-cooled scroll compressor but do not have enough data to predict output conditions. At the moment, I can collect inlet and discharge pressure, outlet temperature, water mass flow rate as well as inlet and outlet temperature. I would like to be able to...

Can we use same refrigerant for both air conditioner and refrigerator?

Hi! For our class project, we have to design a system that freezes an amount of water as quick as possible. The refrigerant is R134a. The compressor is known. I don't really know how to get started here. How do I choose the evaporator pressure and the superheating, and equally the condensor...

I'm graduated in mechanical engineering. I would like to do MS on Refrigeration from USA. Then I would like to focus on design fields. But currently I'm working in the field of steel structure erection. Hope your suggestions and advices to change career.

I am a little confused, because I know how refrigerators work with a refrigerant and a compressor and heat exchanges, and I am looking to build one myself, just wondering because I was looking for refrigerator compressors online to buy. Do they have an inlet for refrigerant or is the...

Hi all, The process of throttling in refrigeration is taken to be isenthalpic. And as enthalpy remains constant then so should the temperature. But in the TS diag of the process it shows a drop of temperature from Thigher to Tlower. Please help me regarding this. Thanks!

Greetings, I wonder what are the usual thermal efficiency for vapor compressor (refrigeration cycle), and only speaking thermal efficiency. I mean COP describes the heat energy pumped vs. work put in. But since some of the work is converted to mechanical energy and to other forms than heat...

I need convincing that evaporative cooling is refrigeration in the sense of a heat engine run backwards. It has the outward appearance of refrigeration. Take perspiration, for example. Your body temperature drops even though the ambient air temperature is hotter. It requires work. You need a...

Hello people I need your help. I am kind new to refrigeration and I want to design one. I have a waste exhaust heat from the Exhaust of the tunnel oven that I have designed. Now I want to use that waste heat as the heat source for the Absorption refrigerator. Q1: what's the best solution I...

When you have a perfect compressor the compression will follow an isentropic line and an h,log(p)-diragram (enthalpy,pressure diagram) but why? What is entropy exactly and what does it mean in such a system? In real life the compressors have an isentropic efficiency of maybe 0.8, which will...

Homework Statement The graph below (see attached) shows the measured magnetization against temperature at room pressure for the material Gd and for another material for use in a magnetic refrigerator at room temperature. 1)Calculate the expected change of temperature of a thermally isolated...

This question has got me quite confused, some guidance would be really appreciated. A room is to be kept at 23C using a heat pump from ambient. Heat gain to the room is 1.5kW per degree Celsius difference between the atmosphere and the room. 1) If the outside temperature is 32C, what is the...

Dear all, Does anyone know common symbols used to represent the ratio of two surface areas? The ratio is the surface area of low temp. heat exchanger divided by the total surface area of low and high temp. heat exchanger: AL/AT = area ratio, i want to find or create a symbol for. I would...

Hi There Based on a Vapour compression refrigeration system: Does anyone out there know a good estimate or any real values for the total heat transfer area for the hot and cold sides of a domestic refrigeration system? i.e. the sum of the areas of the evaporator and the condenser. For the...

Hi There Does anyone out there know a good estimate or any real values for the total heat transfer area for the hot and cold sides of a domestic refrigeration system? i.e. the sum of the areas of the evaporator and the condenser. For the Evaporator: QL=UL.AL.(TL-T1) AL=heat transfer...

I got a pretty basic question about the thermodynamics of air cooling water. I have a liquid cooling system for my CPU, and my monitor currently has my CPU temperature at 14C, which translates somewhere in the range of the high 50s F. I keep my house at 78F during the summer. Is it possible...

In vapor compression refrigeration, I know how to calculate the work done by the compressor (enthalpy at outlet - enthalpy at inlet), but I am lost on how to calculate the work done by the evaporator, condenser, and the expansion valve. For the evaporator and condenser, if I wish to have a...

Hi, I'm curious about doing a middle school science fair project showing how magnetism can be used to cool Gadolinium and thus demonstrate the basis of magnetic refrigeration (ADR). From what I've read it looks like the requirements for generating the required magnetic field would make such...

Homework Statement A conventional vapor-compression refrigeration cycle uses ammonia as the refrigerant. Evaporation and condensation are at -4°C and 34°C respectively and the refrigeration rate is 5kW. The compressor efficiency is 0.75. Assume that the throttle process is isenthalpic...

Homework Statement A nuclear power plant generates 2000 MW of heat energy from nuclear reactions in the reactor's core. This energy is used to boil water and produce high-pressure steam at 300° C. The steam spins a turbine, which produces 700 MW of electric power, then the steam is condensed...

1. Homework Statement A refrigerator is to freeze 150g of water at 0°c in one minute, the ambient temperature being 20°C. Calculate in Watts the minimum power required? So known stuff: mass of water =0.15kg Temp of cold reservoir= 273k Temp of warm reservoir= 293k Specific heat capacity...

So I get that when the VP is equal to atmospheric pressure of 14.7 psia, if you will be at a saturated liquid and when more heat is added, it is latent head changing it to a gas. If however you are at a closed container where the can physically alter the "atmospheric pressure" in the container...

Estimate how long a time it will take to cool a trailer filled with coke ? Given the ambient temperature is 22 degrees C and heat transfer provided by the refrigeration unit is 10 kW and the drinkable temperature is 4 degrees C. Make reasonable estimates of how much insulation is included on...

i have calculated the coefficient of performance COP for both COP ideal and COP from p-h diagram. But the COP ideal i get is lower than the COP i calculated from p-h diagram. is it possible? please help :)

Consider a heat pump works on the vapor-compression refrigeration cycle with 0.2 kg/s of refrigerant-134a as the working fluid. The cycle is used to maintain a house at 26oC while absorbing heat from the outdoors at 3oC. R-134a enters the compressor at 200 kPa as a saturated vapor and leaves at...

Homework Statement A glass manufacturer operates 11 months of the year and produces 97,000 tons of glass per year that needs to be cooled to ambient temperatures. The melting point of glass is 1673K and ambient temperature is assumed to be 293K. The specific heat capacity of glass is 0.837...