U.S. patent application number 15/686739 was filed with the patent office on 2018-02-15 for ideal liquid compression refrigeration cycle.
The applicant listed for this patent is Khaled Mohammed HOSSAIN. Invention is credited to Khaled Mohammed HOSSAIN.
Application Number | 20180045440 15/686739 |
Document ID | / |
Family ID | 56787899 |
Filed Date | 2018-02-15 |
United States Patent
Application |
20180045440 |
Kind Code |
A1 |
HOSSAIN; Khaled Mohammed |
February 15, 2018 |
Ideal Liquid Compression Refrigeration Cycle
Abstract
Liquid compression refrigeration cycle (LCRC) is a new cycle,
that can be applied in the refrigeration and heat pump
applications, this cycle has achieved the coefficient of
performance of the reversed Carnot cycle, unlike the vapor
compression cycle, where a clear deviation from the reversed Carnot
cycle is appeared in it's ideal case, these deviations from the
reversed Carnot cycle have been solved in the Liquid Compression
Cycle (LCRC) to achieve a thermal efficiency more than the Vapor
Compression Cycle (VCRC) efficiency.
Inventors: |
HOSSAIN; Khaled Mohammed;
(Nasr City, EG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HOSSAIN; Khaled Mohammed |
Nasr City |
|
EG |
|
|
Family ID: |
56787899 |
Appl. No.: |
15/686739 |
Filed: |
August 25, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EG2015/000005 |
Feb 25, 2015 |
|
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15686739 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 23/00 20130101 |
International
Class: |
F25B 23/00 20060101
F25B023/00 |
Claims
1. The Liquid compression refrigeration cycle (LCRC). Liquid
compression refrigeration cycle (LCRC) is a new operating theory
for refrigeration and heat pump applications derived from the idea
of the reversed Carnot cycle, the cycle is consisting of 5
processes, 3 isentropic processes, one isothermal process, and one
isobaric process, the cycle (T-H) and (T-S) diagrams are shown in
FIG. 1. Process (1-2) isentropic compression in a liquid pump
Process (2-3) isentropic expansion in a nozzle Process (3-4)
isothermal heat absorption in an evaporator coil Process (4-5)
isentropic compression in a diffuser Process (5-1) isobaric heat
rejection in a condenser coil
2. LCRC components a) Pump b) Nozzle c) Evaporator coil d) Diffuser
e) Condenser coil
3. LCRC theory of operation Liquid compression cycle is working
between 3 levels of pressure, the refrigerant enter the pump at
state 1 as a saturated liquid and compressed from the condenser
pressure to a higher level pressure, then the refrigerant enters
the expansion nozzle to reach the evaporator pressure, during this
expansion process the refrigerant lose a lot of internal energy as
well as the pressure is decreasing during the expansion, these
amount of energy is converted to kinetic energy at state 3, then
the refrigerant is absorbing heat during the isothermal process in
the evaporator to reach state 4 in a 2 phase region, then the
pressure is regained in the diffuser by converting a part of the
kinetic energy again to enthalpy, the refrigerant is isentropic
compressed to the condenser pressure at state 5, then the heat is
rejected to the ambient at constant pressure to enter the pump
again at state 1, FIG. 4 is showing a schematic diagram for the
cycle main components.
4. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to the mechanical power
engineering for refrigeration and heat pumps.
BACKGROUND OF THE INVENTION
[0002] Refrigeration cycles transfer thermal energy from a region
of low temperature to one of higher temperature, the reversed
Carnot cycle is the perfect model for the refrigeration cycle
operating between two fixed temperatures, the most ideal cycle,
which has the maximum thermal efficiency, maximum coefficient of
performance, and serves as a standard against which actual
refrigerator cycles can be compared, reversed Carnot cycle consist
of 4 processes, 2 isentropic processes for expansion and
compression, and 2 isothermal processes for heat rejection and heat
absorption.
[0003] Now most of the refrigerators and heat pumps are working on
the principle of the ideal Vapor compression cycle, that cycle was
built on the principals of the reversed Carnot cycle, but this
cycle is deviate from the reversed Carnot for the following
reasons: [0004] 1--The refrigerant shall enter the compressor at
the vapor phase, for the compressor operation. [0005] 2--Throttling
valve is used in expansion process (constant enthalpy process)
[0006] 3--The heat rejection and absorption at a constant pressure
process, for more practicality.
SUMMARY OF INVENTION
[0007] The intent of this invention is to prove a new ideal
refrigerator cycle (the Liquid compression cycle) which has a
coefficient of performance higher than the Vapor compression
cycle.
Technical Problems
[0008] The coefficient of performance for the ideal Vapor
compression refrigeration cycle (VCRC) is lower than the reversed
Carnot cycle due to the deviation of its ideal process from the
reversed Carnot, this means that the ideal VCRC will consume more
electric power than the reversed Carnot cycle at the same
refrigeration capacity or when the two cycles are operating at the
same maximum and minimum temperatures.
[0009] Moreover, all issues related to the compressors in the
actual VCRC, for example the maintenance, lubrication system, and
it's high cost, etc.
Problems Solution
[0010] The liquid refrigerant pump in the liquid compression
refrigeration cycle (LCRC) is acting the same function of the
compressor in the VCRC to solve all the above problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 showing the LCRC on T-S and T-H diagram.
[0012] FIG. 2 showing the COP levels for Carnot, LCRC, and
VCRC.
[0013] FIG. 3 showing the VCRC on T-S and T-H diagrams.
[0014] FIG. 4 showing a simple schematic diagram for the main
components.
DETAILED DESCRIPTION
[0015] Liquid compression cycle (LCRC) is a cycles, that can be
applied in the refrigeration and heat pumps applications, this
cycle has achieved the performance of the reversed Carnot cycle,
unlike the vapor compression cycle, where a clear deviation from
the reversed Carnot cycle is appeared in it's ideal case, the
deviation is occur due to the compression process where the
refrigerant has to be compressed to a temperature higher than the
condensing temperature, and the constant enthalpy process in the
expansion valve, where energy loss has occurred due to the
irreversibility of the process, these deviations from Carnot cycle
have been solved in the Liquid Compression Cycle (LCRC) to achieve
a thermal efficiency more than the Vapor Compression Cycle (VCRC)
efficiency, and we will prove that later.
[0016] Liquid compression cycle consists of 5 processes, 3
isentropic processes, one isothermal process, and one isobaric
process, the cycle (T-H) and (T-S) diagrams are shown in FIG.
1.
[0017] Process (1-2) isentropic compression in a liquid pump
[0018] Process (2-3) isentropic expansion in a nozzle
[0019] Process (3-4) isothermal heat absorption in an
evaporator
[0020] Process (4-5) isentropic compression in a diffuser
[0021] Process (5-1) isobaric heat rejection in a condenser
[0022] Liquid compression cycle is working between 3 levels of
pressure, the refrigerant enter the pump at state 1 as a saturated
liquid and compressed from the condenser pressure to a higher level
pressure, then the refrigerant enters the expansion nozzle to reach
the evaporator pressure, during this expansion process the
refrigerant lose a lot of internal energy as well as the pressure
is decreasing during the expansion, these amount of energy is
converted to kinetic energy at state 3, then the refrigerant is
absorbing heat during the isothermal process in the evaporator to
reach state 4 in a 2 phase region, then the pressure is regained in
the diffuser by converting a part of the kinetic energy again to
enthalpy, the refrigerant is isentropic compressed to the condenser
pressure at state 5, then the heat is rejected to the ambient at
constant pressure to enter the pump again at state 1, FIG. 4 is
showing a schematic diagram for the cycle main components.
Example
[0023] The following example is showing how the Liquid compression
cycle has achieved the performance of the reversed Carnot cycle
comparing with the Vapor compression cycle at the same levels of
condenser and evaporator pressure.
[0024] As shown in FIG. 2 a comparison between Carnot, LCRC, and
VCRC according to the COP levels
[0025] Assume refrigerant 134a in the Liquid compression cycle is
working between the condenser pressure P.sub.1=1.2 Mpa, and the
evaporator pressure P.sub.3=0.36 Mpa, with refrigerant effect 14
kJ/(kg of refrigerant), now, we can describe and calculate the
properties at each state. [0026] @state 1: saturated liquid phase,
P.sub.1=1.2 Mpa, T.sub.1=46.degree. C., =117.77 kj/kg,
s.sub.1=0.424 kj/kg. K, v.sub.1=0.00089 m3/kg. [0027] @state 2:
sub-cooled phase, P.sub.2 shall be calculated by applying the
energy equation on the total cycle, as follows:
[0027] w.sub.p=q.sub.co-q.sub.ev=(T.sub.1-T.sub.3).DELTA.s
And,
.DELTA.s=14/(5.8+273)=0.05 KJ/Kg
Hence,
w.sub.p=(46-5.8)0.05=2.01 KJ/Kg
But,
w.sub.p=v.sub.1(P.sub.2-P.sub.1)
P.sub.2=(2.01/0.00089)+1200=3458 Kpa=3.46 Mpa
For isentropic compression, s.sub.2=s.sub.1=0.424 KJ/KgK
And,
h.sub.2=v.sub.1(P.sub.2-P.sub.1)+h.sub.1=0.00089(3458-1200)+117.77=119.8
KJ/Kg [0028] @state 3: P.sub.3=0.36 Mpa, for isentropic expansion
s.sub.2=s.sub.3=0.424 KJ/KgK, T.sub.3=5.8.degree. C.,
x.sub.3=0.275,
h.sub.3=h.sub.f+x.sub.3h.sub.fg=59.72+(0.275.times.194.08)=113.1
kj/kg. [0029] @state 4: P.sub.4=P.sub.3=0.36 Mpa, calculating
s.sub.4=.DELTA.s+s.sub.3=0.424+0.05=0.474 kj/kgK, x.sub.4=0.347,
calculating
h.sub.4=h.sub.f+x.sub.4h.sub.fg=59.72+(0.347.times.194.08)=127.04
kj/kg [0030] @state 5: P.sub.5=P.sub.1=1.2 Mpa, for isentropic
compression s.sub.5=s.sub.4=0.474 kj/kgK, x.sub.5=0.1015,
h.sub.5=h.sub.f+x.sub.5h.sub.fg=117.77+(0.102.times.156.1)=133.61
kj/kg [0031] Assume that the ideal Vapor Compression cycle (VCRC)
is working at the same evaporator and condenser pressure as shown
in FIG. 3: [0032] @state 1: P.sub.1=1.2 Mpa, h.sub.1=117.77 kj/kg
[0033] @state 2: at throttling process, h.sub.2=h.sub.1=117.77
kj/kg [0034] @state 3: P.sub.3=0.36 Mpa, h.sub.3=253.81 kj/kg,
s.sub.3=0.9283 kj/kg [0035] @state 4: for isentropic compression
s.sub.4=s.sub.3=0.928 kj/kgK, T.sub.4=50.degree. C., P.sub.4=1.2
Mpa, h.sub.4=278.27 kj/kg
[0036] A--the Coefficient of Performance (COP) for the Rev. Carnot,
LCRC, and VCRC:
COP.sub.carnot=T.sub.3/(T.sub.1-T.sub.3)=278.8/(46-5.8)=7
COP.sub.LCC=q.sub.ev/w.sub.p=14/2=7
COP.sub.VCC=q.sub.ev/w.sub.c=(h.sub.3-h.sub.2)/(h.sub.4-h.sub.3)=136.04/-
24.46=5.56
[0037] B-- Special Configuration of the Nozzle and Diffuser Devices
for the LCRC:
[0038] In the theoretical study of the liquid compression cycle,
special considerations into nozzle and diffuser shall be
considered:
i. Diffuser Inlet Velocities
[0039] Defining the relation between the inlet and outlet
velocities by applying the energy balancing equation on the
diffuser,
h.sub.4+(V.sub.4.sup.2/2)=h.sub.5+(V.sub.5.sup.2/2),
(V.sub.4.sup.2/2)-(V.sub.5.sup.2/2)=.DELTA.h.sub.D
[0040] Dividing the two terms by (V.sub.4.sup.2/2)
1 - V 5 2 V 4 2 = 2 .DELTA. h D V 4 2 V 5 V 4 = 1 - 2 .DELTA. h D V
4 2 ( 1 a ) ##EQU00001##
[0041] Defining the relation between the inlet and outlet
velocities by applying the mass balancing equation on the
diffuser,
A 5 V 5 v 5 = A 4 V 4 v 4 V 5 V 4 = v 5 v 4 A 4 A 5 = ( 2 a )
##EQU00002##
[0042] From equation (1a) and (2a)
v 5 v 4 A 4 A 5 = 1 - 2 .DELTA. h D V 4 2 Then , V 4 = 2 .DELTA. h
D 1 - v 5 2 v 4 2 A 4 2 A 5 2 ( 3 a ) ##EQU00003##
[0043] By substituting in equation 3, where,
[0044] v.sub.4=0.0202 m3/kg, and v.sub.5=0.0025 m3/kg (From the
previous example)
V 4 = 2 .DELTA. h D 1 - 0.0153 A 4 2 A 5 2 ##EQU00004##
[0045] But from the above relation, we found that;
1 - 0.0153 A 4 2 A 5 2 .apprxeq. 1 ##EQU00005##
[0046] Hence,
V.sub.4.apprxeq. {square root over (2.DELTA.h.sub.D)} (4a)
ii. Nozzle Outlet Velocities
[0047] Defining the relation between the inlet and outlet
velocities by applying the energy balancing equation on the
diffuser,
h.sub.2+(V.sub.2.sup.2/2)=h.sub.3+(V.sub.3.sup.2/2),
(V.sub.3.sup.2/2)-(V.sub.2.sup.2/2)=.DELTA.h.sub.N
[0048] Dividing the two terms by (V.sub.2.sup.2/2)
1 - V 2 2 V 3 2 = 2 .DELTA. h N V 3 2 V 2 V 3 = 1 - 2 .DELTA. h N V
3 2 ( 1 b ) ##EQU00006##
[0049] Defining the relation between the inlet and outlet
velocities by applying the mass balancing equation on the
diffuser,
A 3 V 3 v 3 = A 2 V 2 v 2 V 2 V 3 = v 2 v 3 A 3 A 2 ( 2 b )
##EQU00007##
[0050] From equation (1b) and (2b)
v 2 v 3 A 3 A 2 = 1 - 2 .DELTA. h N V 3 2 Then , V 3 = 2 .DELTA. h
D 1 - v 2 2 v 3 2 A 3 2 A 2 2 ( 3 b ) ##EQU00008##
[0051] By substituting in equation 3b,
[0052] Where,
[0053] v.sub.3=0.016 m3/kg, and v.sub.2=0.00089 m3/kg (From the
previous example)
V 3 = 2 .DELTA. h N 1 - 0.003 A 3 2 A 2 2 ##EQU00009##
[0054] From the above equation, we find that;
1 - 0.003 A 3 2 A 2 2 .apprxeq. 1 ##EQU00010##
[0055] Hence,
V.sub.3.apprxeq. {square root over (2.DELTA.h.sub.N)} (4b)
[0056] C-- General Configuration on the Actual Liquid Compression
Cycle: [0057] 1. As shown in the previous example the higher
pressure level is calculated according to the minimum potential
work needed for the reversible Liquid compression cycle, in the
actual cycle, that pressure shall be increased to overcome all
irreversibilities in the cycle. [0058] 2. The expansion process
occur in the nozzle will be adiabatic irreversible process,
where;
[0058] .eta. is . N = .DELTA. h act .DELTA. h is = ( Actual Kinetic
energy at exit ) / ( Isentropic Kinetic energy at exit ) = V act 2
V is 2 ##EQU00011## [0059] 3. The compression process occur in the
diffuser will be adiabatic irreversible process, where;
[0059] .eta. is . D = .DELTA. h is .DELTA. h act = ( Isentropic
Kinetic energy at exit ) / ( Actual Kinetic energy at exit ) = V is
2 V act 2 ##EQU00012## [0060] 4. The compression process occur in
the pump will be adiabatic irreversible process. [0061] 5. A
pressure drop shall occur in evaporator and condenser coil, the
same as the actual Vapor compression cycle.
[0062] Advantages of the Liquid Compression Cycle on the Vapor
Compression Cycle: [0063] 1. The coefficient of performance of LCRC
is higher than VCRC. [0064] 2. If the refrigerant leaving the
condenser in the sub-cooled region, or state 1 is fall in the
sub-cooled region, the COP of the LCRC will slightly raised above
the reversed Carnot cycle, the limitation for this raise depending
on the minimum temperature approach between the refrigerant and the
ambient or the cooling medium. [0065] 3. The work addition process
is occur in the liquid phase, thus the actual process will be close
to the isentropic process, unlike the VCRC, the work addition
process in the superheat region, where more irreversibility has
occur in the actual cycle. [0066] 4. The constant enthalpy process
in the expansion valve for the VCRC, increasing the irreversibility
in the ideal VCRC cycle, as well as, the actual cycle, where there
no expansion valve throttling process in the LCRC. [0067] 5. The
low refrigerant velocity for the vapor line and condenser coil,
will decreasing the friction loss in pipes, and hence the
irreversibility (or energy loss) will decrease in LCRC comparing
with VCRC. [0068] 6. The lubrication system challenges in the VCRC
are not exist in the LCRC by separating the lubricant from the
refrigerant path. [0069] 7. The LCRC is more economic than VCRC in
maintenance, by replacing the compressor with pump for work
addition process. [0070] 8. The initial cost of LCRC is lower than
VCRC in the reason of using pump instead of the compressor.
[0071] Disadvantages of the Liquid Compression Cycle on the Vapor
Compression Cycle [0072] 1. The required refrigerant mass flow rate
is much higher than VCRC for the same evaporator capacity however
this increasing in mass flow rate will not affecting on the total
volume of the cycle, that because the density of the liquid stat is
much higher than density at vapor stat, so the volume of the pump
will not increasing as compressors at higher refrigerant mass flow
rate, in addition the decreasing in condenser and evaporator effect
(heat transfer in KW/Kg of refrigerant mass) will balance the
increasing in refrigerant mass flow rate in LCRC, so the total
surface area of the condenser and evaporator in LCRC will be close
to the VCRC for the same cycle capacity. [0073] 2. The high
refrigerant velocity for the liquid line and evaporator coil in the
LCRC, will increasing the friction loss in pipes, and hence the
irreversibility (or energy loss) will increased in LCRC comparing
with VCRC, however this energy loss is too low if compared with the
VCRC energy loss as discussed above.
[0074] General Recommendation on the Liquid Compression Cycle:
[0075] 1. The positive displacement pump could be more suitable for
the higher compression ratio compared to the required mass flow
rate. [0076] 2. Installing a refrigerant distributor before the
evaporator and condenser coils to divide the mass flow rate on a
multiple paths, will increase the heat transfer area and decreasing
the refrigerant paths, also the nozzle could be a part of the pump
casing, or installed directly after the pump to insure that the
expansion is occurred suddenly after compression process. [0077] 3.
For preventing cavitations at the centrifugal pump suction line a
pressurized tank shall installed at the pump suction, also the tank
for keeping the condenser, and the suction line at a constant
pressure.
LEGEND
[0077] [0078] LCRC Liquid Compression Refrigeration Cycle [0079]
VCRC Vapor Compression Refrigeration Cycle [0080] T Temperature
[0081] P Pressure [0082] H enthalpy per unit of refrigerant mass
[0083] S entropy per unit of refrigerant mass [0084] w.sub.p
Mechanical pump work per unit of refrigerant mass [0085] w.sub.c
Mechanical compressor work per unit of refrigerant mass [0086]
q.sub.co Heat rejected from condenser per unit of refrigerant mass
[0087] q.sub.ev Heat absorbed to evaporator per unit of refrigerant
mass [0088] COP Coefficient Of Performance [0089] X Mass quality,
the ratio of the vapor mass to the total mass of the mixture.
[0090] .DELTA.h.sub.N Total Enthalpy difference in the
diversion-conversion nozzle [0091]
.DELTA.h.sub.N=.DELTA.h.sub.N2-.DELTA.h.sub.N1 [0092]
.DELTA.h.sub.N1 Enthalpy difference in the diversion section of the
diversion-conversion nozzle [0093] .DELTA.h.sub.N2 Enthalpy
difference in the conversion section of the diversion-conversion
nozzle [0094] .DELTA.h.sub.D Total Enthalpy difference in the
diversion-conversion diffuser [0095]
.DELTA.h.sub.D=.DELTA.h.sub.D1-.DELTA.h.sub.D2 [0096]
.DELTA.h.sub.D1 Enthalpy difference in the diversion section of the
diversion-conversion diffuser [0097] .DELTA.h.sub.D2 Enthalpy
difference in the conversion section of the diversion-conversion
diffuser [0098] P Pump. [0099] N Nozzle. [0100] D Diffuser. [0101]
CO Condenser coil. [0102] EV Evaporator coil. [0103]
.DELTA.h.sub.act Actual enthalpy difference [0104] .DELTA.h.sub.is
Isentropic enthalpy difference [0105] V.sub.act.sup.2/2 Actual
Kinetic energy [0106] V.sub.is.sup.2/2 Isentropic Kinetic energy
[0107] .eta..sub.is,N Isentropic efficiency of the nozzle [0108]
.eta..sub.is,D Isentropic efficiency of the diffuser
* * * * *