TRANSPORTATION REFRIGERATION UNIT

Abstract

Operating a transportation refrigeration unit (15) powered by a gas engine includes vaporising liquefied natural gas; and combusting the vaporised liquefied natural gas in the gas engine to power the transportation refrigeration unit (15). The transportation refrigeration unit (15) is used to refrigerate a cargo space (7) onboard a transportation refrigeration system (1).

Claims

1. A method of operating a transportation refrigeration unit (15) powered by a gas engine, the method comprising: vaporising liquefied natural gas; and combusting the vaporised liquefied natural gas in the gas engine to power the transportation refrigeration unit (15).

2. A method as claimed in claim 1, wherein the step of vaporising the liquefied natural gas comprises heating the liquefied natural gas by exchanging thermal energy from refrigerant in a refrigeration circuit (21) of the transportation refrigeration unit (15) to the liquefied natural gas using a heat exchanger (24; 31).

3. A method as claimed in claim 1, wherein the transportation refrigeration unit (15) comprises a (the) refrigeration circuit (21), and wherein the refrigerant circuit comprises one or more of: a refrigerant compressor (29), a condenser (23) and optionally one or more associated condenser fans (23a), an expansion device (25), an evaporator (27) and optionally one or more associated evaporator fans (27a); and wherein the step of combusting the vaporised liquefied natural gas in the gas engine to power the transportation refrigeration unit (15) comprises providing power to the one or more components of the refrigeration circuit (21).

4. A method as claimed in claim 1, wherein the transportation refrigeration unit (15) comprises the gas engine.

5. A method as claimed in claim 1, wherein the transportation refrigeration unit (15) is mounted to a transportation refrigeration system (1) and is in operative association with a cargo space (7) defined within the transportation refrigeration system (1), and wherein the method comprises, subsequent to the step of combusting the vaporised liquefied natural gas in the gas engine to power the transportation refrigeration unit (15), refrigerating a cargo space (7) of the transportation refrigeration system (1) with the transportation refrigeration unit (15).

6. A method as claimed in claim 1, comprising combusting compressed natural gas in the gas engine to power the transportation refrigeration unit.

7. An apparatus comprising: a transportation refrigeration unit (15); a gas engine configured to power the transportation refrigeration unit; and a vaporiser (24; 31) in fluid communication with the gas engine; wherein the vaporiser (24; 31) is configured to vaporise liquefied natural gas into a gaseous state; and wherein the gas engine is configured to combust natural gas in a gaseous state that is received from the vaporiser to power the transportation refrigeration unit (15).

8. An apparatus according to claim 7, wherein the transportation refrigeration unit (15) comprises the gas engine.

9. An apparatus according to claim 7, wherein the vaporiser comprises a heat exchanger (24; 31) that is arranged to heat the liquefied natural gas to vaporise the liquefied natural gas into a gaseous state, wherein the heat exchanger (24; 31) is comprised as part of a refrigeration circuit (21) of the transportation refrigeration unit, and wherein the heat exchanger (24; 31) is arranged to exchange thermal energy from refrigerant in the refrigeration circuit (21) to the liquefied natural gas to thereby heat and vaporise the liquefied natural gas.

10. An apparatus as claimed in claim 7, wherein the gas engine is configured to combust compressed natural gas to power the transportation refrigeration unit (15).

11. An apparatus as claimed in claim 7, comprising a liquefied natural gas storage tank (17) in communication with the vaporiser (24) and configured to supply liquefied natural gas thereto.

12. A transportation refrigeration system (1) comprising an apparatus in accordance with claim 7.

13. A transportation refrigeration system (1) according to claim 12, wherein the transportation refrigeration system is a refrigerated vehicle (1) or a refrigerated trailer (5) of a vehicle.

14. A transportation refrigeration system (1) according to claim 12, wherein the gas engine configured to power the transportation refrigeration unit (15) is a first engine and the transportation refrigeration system (1) comprises a second engine (9) that is a primary, motive engine for powering motion of the transportation refrigeration system (1).

15. A cold chain distribution system comprising one or more transportation refrigeration systems (1) in accordance with claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Certain embodiments of the invention will now be described, by way of example only, and with reference to the following drawings, in which:

[0040] FIG. 1 depicts a transportation refrigeration system comprising a transportation refrigeration unit according to an embodiment of the invention;

[0041] FIG. 2 is a schematic of components of the transportation refrigeration system and transportation refrigeration unit of FIG. 1; and

[0042] FIG. 3 is a schematic of components of a transportation refrigeration system comprising a transportation refrigeration unit according to an alternative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0043] FIG. 1 shows a transportation refrigeration system 1 in the form of a heavy good vehicle (HGV) 1. The HGV 1 comprises a tractive vehicle 3 and a trailer 5. The trailer 5 defines a cargo space 7 therein. The tractive vehicle 3 comprises a gas engine 9 that acts as the primary motive engine of the tractive vehicle 3/HGV 1. That is, the gas engine 9 provides motive power to a drive shaft (not shown) of the HGV 1 in order to drive its wheels into rotation.

[0044] The gas engine 9 is connected to and in fluid communication with a vehicle liquefied natural gas (LNG) tank 13 via a conduit 11. The LNG tank 13 is configured to store LNG therein and thus is configured to maintain LNG at very low temperatures (e.g. -162° C.), with the exact temperature conditions being determined based on ambient pressure conditions. The vehicle LNG tank 13 acts as a store for fuel (i.e. LNG) for the gas engine 9. Fueling the gas engine 9 such that motive power is provided to the HGV 1 comprises passing LNG from the vehicle LNG tank 13 to the gas engine 9 via conduit 11. During transit in the conduit 11, the LNG is vaporised (through heating or otherwise) into a gaseous form such that it can be suitably introduced into the gas engine 9 for combustion therein to provide motive power to the HGV 1.

[0045] The HGV 1 further comprises a transportation refrigeration unit (TRU) 15 attached to the trailer 5. The TRU 15, as will be described in greater detail below with reference to FIG. 2, is arranged to refrigerate the cargo space 7 defined within the trailer 5. Whilst not shown, the TRU 15 comprises a gas engine that is arranged to provide power for operation of the TRU 15 (and more specifically) to power components of the refrigeration circuit of the TRU 15 as will be described in greater detail below.

[0046] The TRU 15, specifically the gas engine of the TRU 15, is connected to and in fluid communication with a TRU LNG tank 17 via conduit 19. As with the vehicle LNG tank 13, the TRU LNG tank 17 is configured to maintain the LNG at very low temperatures, with the exact temperatures being determined based on ambient pressure conditions. The TRU LNG tank 17 acts as a store for fuel (i.e. LNG) for the TRU as will be described below with reference to FIG. 2.

[0047] FIG. 2 schematically depicts further details of the HGV 1 and the TRU 15. The TRU 15 comprises a refrigeration circuit 21 comprising a condenser 23 fluidly connected upstream of an expansion valve 25, which in turn is fluidly connected upstream of an evaporator 27. The evaporator 27 is fluidly connected upstream of an accumulator 29a that feeds a compressor 29, which in turn is fluidly connected upstream of the condenser 23 to complete the refrigeration circuit 21. A receiver 28 is also situated within the refrigeration circuit 21. The evaporator 27 and condenser 23 are each associated with an evaporator fan 27a and condenser fan 23a, respectively that are each configured to promote the flow of air over and thereby the heat transfer at the evaporator 27 and condenser 23.

[0048] Additionally, positioned within the refrigeration circuit 21, downstream of the condenser 23 and upstream of the expansion valve 25, are a first heat exchanger 24 and, downstream thereof, a second heat exchanger 26. A filter drier 32 is also positioned upstream of the first heat exchanger 24 and downstream of the condenser.

[0049] The second heat exchanger 26 is legacy heat exchanger 26 that is configured to place refrigerant upstream of the expansion valve 25 into thermal communication exchange with refrigerant downstream of the evaporator 27.

[0050] The first heat exchanger 24, further details of which are shown in the enlarged view at the top right of FIG. 2, comprises an inlet 24a for refrigerant received from the filter drier 32 and condenser 23. The inlet 24a is fluidly connected to an outlet 24b for refrigerant to pass to the second heat exchanger 26. The first heat exchanger 24 further comprises an inlet 24c connected to the TRU LNG tank 17 via a first part of conduit 19. The inlet 24c is in fluid communication with an outlet 24d which in turn is fluidly connected to the TRU 15 via a second part of the conduit 19.

[0051] The second heat exchanger 26, the expansion valve 25 and the evaporator 27 are positioned within the cargo space of the 7 of the trailer 5 and are configured, in particular the evaporator 27 and evaporator fan 27a is configured, to refrigerate the cargo space 7.

[0052] The compressor 29, condenser 23 and first heat exchanger 24 are situated external to the cargo space in a condensing unit 30 of the TRU 15.

[0053] In use, the components of the refrigeration circuit 21, and in particular the compressor 29, the condenser fan 23a and the evaporator fan 27a are powered into operation by the gas engine of the TRU 15.

[0054] Operation of the compressor 29 pressurises gaseous refrigerant in the circuit 21 and sends said refrigerant downstream to the condenser 23 where the refrigerant is condensed into a liquid state through thermal exchange with air that is blown over the condenser 23 via the condenser fan 23a. The refrigerant is then circulated via the filter drier 32 to the first heat exchanger 24 to cool further and exchange thermal energy with LNG (more on this below) and to then to the second heat exchanger 26 where the refrigerant undergoes thermal exchange with refrigerant from downstream of the evaporator 27. The refrigerant is then passed to the expansion valve 25 for expansion, before being passed to the evaporator 27 where the refrigerant vaporizes through thermal exchange with the air in the cargo space 7 that is blown over the evaporator 27 by the evaporator fan 27a. This vaporisation of the refrigerant in the evaporator 27 results from the withdrawal of thermal energy from the air in the cargo space 7, which in turn results in a cooling/refrigeration of the cargo space 7.

[0055] The refrigerant is then output from the evaporator 27 where it is sent back through the second heat exchanger 26 for thermal exchange with refrigerant upstream of the expansion valve 25, before being output back via the accumulator 29a to the compressor 29 to be recirculated around the refrigeration circuit 21 again for further continued cooling of the cargo space 7.

[0056] The gas engine of the TRU 15 which powers operation of the refrigeration circuit 21 of the TRU 15 is fueled by supplying LNG from the TRU LNG tank 17 via the conduit 19 to the engine of the TRU 15. Before the LNG can be combusted in the gas engine of the TRU 15 however, it is vaporised into a gaseous form such that it is suited for combustion in the TRU 15 gas engine. This vaporisation is undertaken in the first heat exchanger 24. LNG from the TRU LNG tank 17 is fed by a first part of the conduit 19 into the inlet 24c of the heat exchanger 24 wherein the LNG is vaporised through thermal exchange with the refrigerant passing through the heat exchanger 24 from the condenser 23. Once vaporised, the vaporised LNG is output via the outlet 24d and is sent in its gaseous form for combustion in the combustion engine of the TRU 15.

[0057] By using the heat exchanger 24 to vaporise the LNG, not only is the LNG converted into a form that permits its combustion as a fuel for the gas engine of the TRU 15 but simultaneously the performance of the refrigeration circuit 21 is improved since additional waste heat from the refrigerant is removed to ensure cooled refrigerant is being passed to the evaporator 27 which ensures improved cooling of the cargo space 7.

[0058] FIG. 3 shows components of a transportation refrigeration system comprising a transportation refrigeration unit (TRU) according to an alternative embodiment. The features and components of the transportation refrigeration unit and the transportation refrigeration system of FIG. 3 are largely the same as the features and components of the HGV 1 and the transportation refrigeration unit 15 described above in relation to FIGS. 1 and 2. Correspondent features have thus been denoted with like reference numerals and a detailed description of these features will not be repeated again here.

[0059] Where the TRU 15 and the transportation refrigeration system of FIG. 3 differ from the TRU 15 and HGV 1 of FIGS. 1 and 2 is that the first heat exchanger 24 and second heat exchanger 26 have been replaced in the refrigeration circuit 31 by a single combined type heat exchanger 31 that is positioned within the cargo space 7. The combined heat exchanger 31 provides the functionality of both the first and the second heat exchangers 24, 26 of the embodiment as described in relation to FIGS. 1 and 2. That is, the combined heat exchanger 31 both provides for thermal exchange between refrigerant upstream of the expansion valve 25 and refrigerant downstream of the evaporator 27, and additionally provides for thermal exchange between refrigerant upstream of the expansion valve 25 and LNG passing from the TRU LNG tank 17 and the gas engine of the TRU 15.

[0060] Further details of the combined heat exchanger 31 can be seen enlarged in the top right of FIG. 3. As shown, the heat exchanger comprises three inlets 31a-31c and three outlets 31d-31f.

[0061] The inlet 31a is fluidly connected downstream of the condenser 23 and is arranged to receive refrigerant therefrom. The refrigerant received at inlet 31a is passed through the heat exchanger 31 and is output at outlet 31d where it is subsequently sent to an inlet of the expansion valve 25.

[0062] The inlet 31b is fluidly connected downstream of the evaporator 27 and is arranged to receive refrigerant therefrom. The refrigerant received at inlet 31b is passed through the heat exchanger 31 and is output at outlet 31e where it is subsequently sent to the compressor 29.

[0063] The inlet 31c is fluidly connected to the TRU LNG tank 17 via a first part of conduit 19 and is arranged to receive LNG therefrom. The LNG received at inlet 31c is passed through the heat exchanger 31 where it is vaporised through thermal exchange with refrigerant passing through the heat exchanger 31 and is output in gaseous form at outlet 31f. From the outlet 31f, the vaporised LNG is sent to the gas engine of the TRU 15 for combustion.

[0064] As in the first embodiment, thermal exchange between refrigerant upstream of the expansion valve 25 with LNG upstream of the gas engine of the TRU 15, which in this embodiment is provided for by the combined heat exchanger 31, is advantageous since it simultaneously vaporises the LNG into a gaseous form for combustion in the gas engine of the TRU 15 and removes waste heat from the refrigerant upstream of the expansion valve 25 and evaporator 27 such that improved and more efficient refrigeration can be provided to the cargo space 7.

[0065] In the embodiment of FIG. 3, since the combined heat exchanger 31 is provided in the cargo space 7, a methane detector 33 is provided to detect any natural gas which may have leaked from the combined heat exchanger 31 into the enclosed environment of the cargo space 7. The methane detector 33 can thus provide an alert in the event for free methane such that explosion or asphyxiation risks can be avoided.